Highly conductive graphene fabric and method of making the same

Abstract

The present application provides a high-conductivity graphene-based fabric, comprising graphene composite fibers, the graphene composite fibers comprising graphene and carbon nanotubes (CNT) doped between graphene layers and oriented along the axial direction of the fibers. The present application effectively avoids the formation of fiber surface wrinkles through effective doping of CNT. In addition, the formation of wrinkles after swelling fusion between fibers during post-treatment swelling can also be effectively avoided, ensuring the effectiveness of the electronic transmission path in the graphene fabric, and thus a high-conductivity graphene fabric is prepared. After carbonization treatment at 800 degrees Celsius, the conductivity of the graphene composite fabric is as high as 1 x 10 4 S / m.

Description

Technical Field

[0001] This invention relates to a highly conductive graphene fabric and its preparation method. Background Technology

[0002] Novel carbon-based fabrics play an important role in fields such as biosensing and electronic skin. How to fabricate ultrathin carbon-based fabrics with high conductivity and high flexibility has become an urgent problem to be solved. The inherent conductivity of carbon materials and the fiber overlap pattern of the fabric are the two main factors affecting the conductivity of carbon-based fabrics.

[0003] Graphene is composed of sp 2 A monolayer composed of hybridized carbon atoms has a theoretical conductivity as high as 10⁻⁶. 8 S / m. Therefore, it is considered one of the ideal materials for preparing highly conductive fabrics. However, due to the "second Rayleigh instability" during the electrospinning process, graphene sheets are topologically assembled into hollow fiber structures. This non-dense structure severely affects the conductivity of graphene fabrics. Furthermore, the random overlap between graphene nanofibers results in poor conductivity of graphene fabrics in the direction perpendicular to the surface.

[0004] Seung Kwon Seol's team used 3D ultrafine needle printing technology to prepare dense graphene nanofibers with high conductivity and mechanical strength. However, the prepared nanofibers had problems such as poor orientation of graphene sheets within the fibers and many wrinkles on the fiber surface. This resulted in a reduction in the hole density between graphene sheets within the nanofibers, hindering electron transport and leading to an increase in fiber resistance. In addition, these wrinkles also reduced the fiber contact density between fibers in the fabric, which had a very negative impact on the preparation of highly conductive fabrics. Summary of the Invention

[0005] The purpose of this invention is to address the shortcomings of existing technologies by providing a highly conductive graphene fabric and its preparation method.

[0006] The technical solution of this invention is: a highly conductive graphene-based fiber fabric, comprising graphene composite fibers, wherein the graphene composite fibers include graphene and carbon nanotubes (CNTs) doped between the graphene layers and oriented along the fiber axial direction. This invention, through the effective doping of CNTs, achieves two advantages: firstly, the larger aspect ratio of CNTs increases the chain entanglement density in the solution, providing an elastic modulus G' for the spinning solution, regulating the normal stress difference of the spinning solution, enhancing the spinning solution's ability to resist surface tension and interrupt the fine flow, and increasing the spinnability of the solution; secondly, CNTs are adsorbed around the graphene sheets by van der Waals forces, supporting the structural stability of the graphene sheets, increasing the bending rigidity of the graphene sheets, and enhancing the ability of the graphene oxide sheets to resist shrinkage stress during electrospinning and drying, effectively preventing the formation of wrinkles on the fiber surface. Furthermore, during the post-treatment swelling process, the formation of wrinkles after the swelling and fusion of fibers can also be effectively avoided, ensuring the effectiveness of the electron transport pathway in the graphene fabric, thereby preparing a highly conductive graphene fabric.

[0007] This invention also provides a method for preparing the above-mentioned highly conductive graphene fabric, the method comprising:

[0008] (1) Electrospinning was performed using a mixed dispersion of carbon nanotubes, graphene oxide and polymer as the spinning solution, and the fiber membrane was obtained by collecting it in a ring. The mass ratio of CNTs to GO was 1:1-1:4, and the mass fraction of polymer in the mixed dispersion was 0.5%-1%.

[0009] (2) Swelling and fusion treatment: Soak in 90% ethanol aqueous solution for 3 hours, then remove and dry using a tetrafluoroethylene membrane to obtain composite graphene oxide fabric.

[0010] (3) Carbonization treatment: After the composite graphene oxide fabric is reduced with HI vapor, it is carbonized at 800 degrees Celsius for 1 hour to obtain a highly conductive graphene fabric.

[0011] The spinning solution's "Taylor cone" is subjected to high-multiplication stretching under an electric field. As the liquid flow gradually narrows and the specific surface area increases, the solvent water in the spinning solution evaporates rapidly, and the graphene composite fiber solidifies and forms quickly. During this process, solvent evaporation causes the graphene oxide sheets to interact under the influence of van der Waals forces. Simultaneously, uneven solvent evaporation leads to uneven stress and strain on the graphene sheets, resulting in drying shrinkage of the graphene oxide fibers, wrinkles on the fiber surface, and irregular fiber shape. This morphological structure severely affects the performance of the graphene oxide composite fiber and its fabric. This invention introduces CNTs into the spinning solution system. Because CNTs possess high mechanical strength, Young's modulus, and a large aspect ratio, they not only guide the high orientation of graphene but also fill the voids between graphene oxide sheets and those formed by solvent evaporation within the graphene oxide fiber. This reduces the uneven normal stress on the fiber caused by drying shrinkage, suppresses irregular fiber structure, makes the fiber more rounded, and improves the conductivity within the graphene fabric layer. On the other hand, CNTs can be adsorbed onto the fiber surface by van der Waals forces, improving the wrinkles and grooves on the surface of graphene oxide fibers and making the fiber surface smoother. After swelling and fusion, the effective overlap between fibers in the graphene fabric increases, which is beneficial to improving the interlayer conductivity of the graphene fabric, and finally producing a highly conductive graphene fabric.

[0012] Furthermore, the mass fractions of CNTs and GO in the mixed dispersion are 0.11%-0.13% and 0.11%-0.47%, respectively. This dispersion composition maintains good tensile properties, meeting the requirements for electrospinning and producing graphene fabrics with uniform fiber morphology. Additionally, CNTs can efficiently improve the conductivity of the graphene fabric. Too few CNTs cannot effectively fill and connect the graphene sheets, resulting in an inefficient improvement in the conductivity of the graphene fabric; too many CNTs lead to poor solution tensile properties, failing to meet the requirements for electrospinning and preventing the production of graphene fabrics with uniform fiber morphology.

[0013] Furthermore, the graphene oxide has a size of 5-20 μm. Graphene oxide sheets of this size are more easily bent and stacked into fibers under surface tension, resulting in graphene fabrics with uniform fiber morphology. Smaller graphene sheets cannot be used to prepare continuous graphene fibers, and therefore cannot be assembled into graphene fabrics; larger graphene sheets are difficult to bend and fold into fibers under surface tension, and therefore cannot be assembled into graphene fabrics.

[0014] Furthermore, the carbon nanotubes are single-walled carbon nanotubes with a length of 2-50 μm, a diameter of 1-2 nm, and an electrical conductivity greater than 10. 5 Single-walled carbon nanotubes with a large aspect ratio have low bending stiffness, allowing them to fill the interior and surface of fibers well, and can enhance the conductivity between graphene sheets, thereby improving the conductivity of graphene fabrics.

[0015] Furthermore, the polymer has a weight-average molecular weight greater than 10. 6 The polymer is sodium polyacrylate, PVA, or PEO, or one or more of these. Higher molecular weight polymers can provide sufficient entanglement, improve solution tensile properties, and produce graphene fabrics with uniform fiber morphology.

[0016] Furthermore, the ring is either a metal ring or a graphite ring. This allows for the acquisition of regular fabric patterns, making processing easier. The graphite ring, acting as a receiver, reduces fabric transfer steps and ensures the structural stability of the fabric.

[0017] Furthermore, the chamber temperature for electrospinning is 40-45 degrees Celsius, the humidity is 10-20%, the extrusion rate is 0.01±0.002 ml / min, the distance between the ring and the metal needle is 20±5 cm, and the spinning machine voltage is 10-20 KV. Under these chamber conditions, graphene oxide composite fiber fabrics with uniform morphology can be obtained.

[0018] Furthermore, the spinning solution is prepared by the following method:

[0019] (1) Add 0.15g CNT to 98.5g water and add 0.06g surfactant. After shaking evenly, use a cell disruptor to sonicate for 2-3 hours to prepare a 0.15% CNT solution.

[0020] (2) Take 20g of CNT solution, add 6g of 20.0mg / g GO solution, and add 0.026g of surfactant. Mix well with a planetary mixer.

[0021] (3) Add 0.256g of polymer to the CNT / GO solution to make the polymer content in the solution 1%, and stir mechanically for 24-48h until it is completely dissolved and evenly dispersed to prepare a spinning solution.

[0022] Furthermore, the surfactant is Triton-X100, one of the SDS.

[0023] The beneficial effects of this invention are as follows: after carbonization treatment at 800 degrees Celsius, the conductivity of the graphene composite fabric reaches as high as 1×10⁻⁶. 4 S / m. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of an electrospinning apparatus.

[0025] Figure 2 The image shows the SEM images of the graphene nanofiber fabric without CNTs in Comparative Example 1 and the SEM images of the composite fibers therein.

[0026] Figure 3SEM images of the graphene nanofiber fabric with CNTs added in Example 1 and SEM images of the composite fibers therein.

[0027] Figure 4 The image shows a TEM image of the composite fibers in the graphene nanofiber fabric with added CNTs in Example 1. As can be seen from the image, the CNTs are highly oriented.

[0028] Figure 5 This is a comparison chart of the electrical conductivity of graphene fabrics.

[0029] Figure 6 Added CNT graphene fabric photo. Detailed Implementation

[0030] The present invention will be further described below with reference to the embodiments and accompanying drawings, but is not limited thereto.

[0031] The conductivity of the fabrics described in this invention was obtained by testing using the four-point method (GB / T 24525-2009).

[0032] Example 1

[0033] (1) Take 0.15g of CNTs (length 2-50um, diameter 1-2nm, conductivity 10^ 5 Add S / m (Jiangsu Xianfeng Nanomaterials Technology Co., Ltd.) to 98.5g of water and add 0.06g of surfactant SDS (Shanghai Aladdin Biochemical Technology Co., Ltd.). After shaking evenly, use a cell disruptor to sonicate for 2-3 hours to prepare a 0.15% CNT solution.

[0034] (2) Take 20g of CNT solution, add 6g of 20.0mg / g GO (size 5-20um, Hangzhou Gaoxi Technology Co., Ltd.) solution, and add 0.026g of surfactant SDS. Stir evenly using a planetary mixer; then add 0.256g of polymer PVA (weight average molecular weight 10). 6 (Shanghai Aladdin Biochemical Technology Co., Ltd.) prepared a spinning solution by mixing polymer, GO and CNT in a solution with mass fractions of 1%, 0.47% and 0.11%, respectively, and mechanically stirring for 24-48 hours until completely dissolved and evenly dispersed.

[0035] (3) Use a syringe to take 10g of spinning solution and place it into the electrospinning machine (e.g., ...). Figure 1As shown, a metal needle is attached vertically downwards to the syringe and connected to the positive terminal of the spinning machine voltage. The bottom plate of the spinning machine is made of PTFE. A collecting ring is placed on the PTFE plate, directly below the needle. The chamber temperature for electrospinning is adjusted to 45 degrees Celsius, the humidity to 10%, the extrusion rate to 0.01 ± 0.002 ml / min, the distance between the ring and the metal needle to 20 cm, and the spinning machine voltage to 10 kV. After 60 min, graphene oxide fabric with a thickness < 1 μm is obtained on the collecting ring.

[0036] (4) The graphene oxide composite fabric was transferred to a 90% ethanol (Shanghai Aladdin Biochemical Technology Co., Ltd.) aqueous solution and soaked for 3 hours. Then, it was taken out and dried using a tetrafluoroethylene membrane to obtain the fused graphene oxide fabric.

[0037] (5) The fused graphene oxide fabric was reduced with HI (Shanghai Aladdin Biochemical Technology Co., Ltd.) vapor (70 degrees Celsius, 5 hours), and then treated at 800 degrees Celsius for 2 hours in a tube furnace under an argon atmosphere (purity ≥99.9%, Hangzhou Minxing Chemical Technology Co., Ltd.). The final product was a highly conductive graphene fabric, denoted as CF-1.

[0038] Figure 3 This image shows a SEM image of the composite fibers in the graphene nanofiber fabric prepared in this embodiment. As can be seen from the image, the nanofibers in the fabric have smooth and relatively rounded surfaces. Furthermore, after swelling and fusion, the overlap between the graphene fibers is tighter, increasing the fiber overlap density in the fabric. TEM images are shown below. Figure 4 As shown, under high-strength stretching under an electric field, CNTs and graphene sheets are highly oriented along the fiber axis. Furthermore, the longer CNTs act like "highways," enhancing electron transport between graphene sheets and improving the conductivity of the graphene nanofibers. The conductivity was measured using the four-point method to be 6 × 10⁻⁶. 3 S / m.

[0039] Example 2

[0040] (1) Take 0.15g of CNTs (length 2-50um, diameter 1-2nm, conductivity 10^ 5 Add S / m (Jiangsu Xianfeng Nanomaterials Technology Co., Ltd.) to 98.5g of water and add 0.06g of surfactant Triton-X100 (Shanghai Aladdin Biochemical Technology Co., Ltd.). After shaking evenly, use a cell disruptor to sonicate for 2-3 hours to prepare a 0.15% CNT solution.

[0041] (2) Take 20g of CNT solution, add 1.5g of 20.0mg / g GO (size 5-20um, Hangzhou Gaoxi Technology Co., Ltd.) solution, and add 0.012g of surfactant Triton-X100. Stir evenly using a planetary mixer; then add 0.06g of polymer PEO (weight average molecular weight 6×10). 6 (Shanghai Aladdin Biochemical Technology Co., Ltd.) prepared a spinning solution by mixing polymer, GO and CNT in a solution with mass fractions of 0.5%, 0.11% and 0.13%, respectively, and mechanically stirring for 24-48 hours until completely dissolved and evenly dispersed.

[0042] (3) Use a syringe to take 10g of spinning solution and place it into the electrospinning machine (e.g., ...). Figure 1 As shown, a metal needle is attached vertically downwards to the syringe and connected to the positive terminal of the spinning machine voltage. The bottom plate of the spinning machine is made of PTFE. A collecting ring is placed on the PTFE plate, directly below the needle. The chamber temperature for electrospinning is adjusted to 45 degrees Celsius, the humidity to 10%, the extrusion rate to 0.01 ± 0.002 ml / min, the distance between the ring and the metal needle to 20 cm, and the spinning machine voltage to 10 kV. After 60 min, graphene oxide fabric with a thickness < 1 μm is obtained on the collecting ring.

[0043] (4) The graphene oxide composite fabric was transferred to a 90% ethanol (Shanghai Aladdin Biochemical Technology Co., Ltd.) aqueous solution and soaked for 3 hours. After soaking, it was removed and dried using a tetrafluoroethylene membrane to obtain the fused graphene oxide fabric.

[0044] (5) The fused graphene oxide fabric was reduced with HI (Shanghai Aladdin Biochemical Technology Co., Ltd.) vapor (70 degrees Celsius, 5 hours), and then treated at 800 degrees Celsius for 2 hours in a tube furnace under an argon atmosphere (purity ≥99.9%, Hangzhou Minxing Chemical Technology Co., Ltd.). The final product was a highly conductive graphene fabric, denoted as CF-2.

[0045] The fabric was characterized using the same methods as in Example 1. SEM confirmed that the nanofibers in this example had smooth and relatively rounded surfaces, and the graphene fibers were tightly interlocked. TEM showed that the CNTs and graphene sheets were highly oriented along the fiber axis. The conductivity was measured to be 1×10⁻⁶ using the four-point method. 4 S / m.

[0046] Comparative Example 1

[0047] (1) Add 6g of 20.0mg / g GO solution to 0.026g of surfactant and stir evenly with a planetary mixer; then add 6g of 20.0mg / g polymer to make the polymer content in the solution 1% and stir mechanically for 24-48h until completely dissolved and evenly dispersed to prepare spinning solution.

[0048] (2) Use a syringe to take 10g of spinning solution and place it into the electrostatic spinning machine (e.g., ...). Figure 1 As shown, a metal needle is attached vertically downwards to the syringe and connected to the positive terminal of the spinning machine voltage. The bottom plate of the spinning machine is made of PTFE. A collecting ring is placed on the PTFE plate, directly below the needle. The chamber temperature for electrospinning is adjusted to 45 degrees Celsius, the humidity to 10%, the extrusion rate to 0.01 ± 0.002 ml / min, the distance between the ring and the metal needle to 20 cm, and the spinning machine voltage to 20 kV. After 30 minutes, a composite graphene oxide fabric is prepared on the collecting ring.

[0049] (4) The composite graphene oxide fabric was reduced with HI vapor (Shanghai Aladdin Biochemical Technology Co., Ltd.) at 70°C for 5 hours, and then treated at 800°C for 2 hours in a tube furnace under an argon atmosphere (purity ≥99.9%, Hangzhou Minxing Chemical Technology Co., Ltd.). The resulting graphene nanofiber fabric, denoted as GF, had a conductivity of 2 × 10⁻⁶. 3 S / m.

[0050] The same characterization methods as in Example 1 were used for characterization. Figure 2 SEM analysis revealed numerous and deep wrinkles on the surface of the graphene nanofibers in the fabric prepared in this comparative example. Cross-sectional observation also showed that the GF fibers were irregularly shaped filaments. Combined with the SEM images, the fabric exhibited a loosely spaced fiber structure with significant inter-fiber spacing and minimal effective overlap. This is primarily due to the generation of numerous gas cavities during polymer pyrolysis during thermal processing, leading to the collapse of the graphene sheet assembly structure within the fibers. This results in deep wrinkles on the fiber surface, reducing surface energy and decreasing inter-fiber forces. Furthermore, fiber shrinkage during electrospinning and heat treatment annealing also contributes to the collapse and displacement of the graphene sheet assembly structure, ultimately forming deep wrinkles on the fiber surface. These wrinkles and irregular shapes reduce the electron-hole density within the fabric, hindering efficient electron transport and severely impacting fiber fusion, thus negatively affecting the electrical conductivity of the graphene fabric.

[0051] The above case studies demonstrate that introducing CNTs into the spinning solution system not only guides the high orientation of graphene but also fills voids formed between graphene sheets and by solvent evaporation within the graphene oxide fibers. This results in more rounded fibers, improving the conductivity within the graphene fabric layers. Furthermore, the tight bonding between CNTs and graphene sheets enhances the inter-sheet forces, increases the bending rigidity of the graphene sheets, and supports them. This significantly mitigates structural collapse and displacement of the graphene sheets during fiber forming, swelling, drying, and high-temperature annealing, reducing fiber wrinkles. On the other hand, CNTs can be adsorbed onto the fiber surface by van der Waals forces, improving surface wrinkles and grooves, resulting in a smoother fiber surface. After swelling and fusion, the increased effective overlap between fibers within the graphene fabric further enhances the interlayer conductivity, ultimately producing highly conductive graphene fabrics.

[0052] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a highly conductive graphene fabric, characterized in that, The method is as follows: (1) Electrospinning was performed using a mixed dispersion of carbon nanotubes, graphene oxide and polymer as the spinning solution, and the fiber membrane was obtained by collecting it in a ring. The mass ratio of CNTs to GO was 1:1-1:4, and the mass fraction of polymer in the mixed dispersion was 0.5%-1%. (2) Soak in a 90% ethanol aqueous solution for 3 hours, then remove and dry using a tetrafluoroethylene membrane; (3) After reduction with HI, carbonization at 800 degrees Celsius for 1 hour is performed to obtain highly conductive graphene fabric. The mass fractions of CNT and GO in the mixed dispersion are 0.11%-0.13% and 0.11%-0.47%, respectively. The size of the graphene oxide is 5-20 μm; The carbon nanotubes are single-walled carbon nanotubes with a length of 2-50 μm, a diameter of 1-2 nm, and an electrical conductivity greater than 10^-10. 5 S / m; The polymer has a weight-average molecular weight greater than 10. 6 It is one or more of sodium polyacrylate, PVA, and PEO; The ring is either a metal ring or a graphite ring.

2. The preparation method according to claim 1, characterized in that, The chamber temperature for electrospinning is 40-45 degrees Celsius, and the humidity is 10-20%. The extrusion rate is 0.01±0.002 ml / min, the distance between the ring and the metal needle is 20±5 cm, and the voltage of the spinning machine is 10-20 KV.

3. The preparation method according to claim 1, characterized in that, The spinning solution is prepared by the following method: (1) Add 1.5g CNT to 98.5g water and 6g surfactant, shake well, and then sonicate for 2-3 hours using a cell disruptor to prepare a 1.5% CNT solution. (2) Take 20g of CNT solution, add 6g of 20.0mg / g GO solution, and add 0.026g of surfactant, and stir well; (3) Add 0.256g of polymer to the CNT / GO solution to make the polymer content in the solution 1%, and stir mechanically for 24-48h until it is completely dissolved and evenly dispersed to prepare a spinning solution.

4. The preparation method according to claim 3, characterized in that, The surfactant is one of Triton-X100 and SDS.

5. A highly conductive graphene-based fiber fabric prepared by the method according to any one of claims 1-4, characterized in that, The invention includes graphene composite fibers, which comprise graphene and CNTs doped between graphene layers and oriented along the fiber axial direction.

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