WO2023236351A1

WO2023236351A1 - Graphene assembly fiber, and preparation method therefor and use thereof

Info

Publication number: WO2023236351A1
Application number: PCT/CN2022/113968
Authority: WO
Inventors: 耿凤霞; 徐天琪; 张家文; 嵇锦鹏; 宋兆涛
Original assignee: 苏州大学
Priority date: 2022-06-07
Filing date: 2022-08-22
Publication date: 2023-12-14
Also published as: CN114990734A

Abstract

A graphene assembly fiber, and a preparation method therefor and the use thereof. An aqueous graphene oxide solution used as a spinning solution and an aqueous amine compound solution used as a coagulating bath are subjected to spinning and a reduction treatment to obtain a graphene assembly fiber. In the prior art, annealing at a very high temperature (such as 3000ºC) can eliminate atomic defects on a graphene sheet and promote the formation of graphite microcrystals, thereby improving the tensile strength. The graphene assembly fiber, and the preparation method therefor and the use thereof solve the problem of a high temperature being required for improving the mechanical performance; and the graphene fiber obtained at a low temperature presents very high mechanical properties, has a tensile strength of 3.2 ± 0.2 GPa, a Young's modulus of 290 ± 54 GPa and an electric conductivity of 1.5 * 10⁵ S·m^-1, and is one order of magnitude higher than that of a graphene fiber obtained in the prior art.

Description

A graphene assembly fiber and its preparation method and application

Technical field

The invention belongs to nanosheet assembly technology, and specifically relates to a graphene assembly fiber and its preparation method and application.

Background technique

Because graphene's single-atom thickness and large area give it a large aspect ratio, it can be assembled into macrostructures such as graphene fibers. The starting point for the synthesis of macroscopic graphene is usually graphene oxide (GO) dispersed in a solvent. Fibers are made from dispersed GO through wet spinning technology, and then graphene-based fibers are obtained through chemical or thermal reduction. The existing technology emphasizes the importance of reducing structural defects and improving the regular arrangement of graphene sheets to improve the mechanical and electrical properties of graphene fibers. The tensile strength of the initially obtained chemically reduced graphene oxide fibers was about 200 MPa, recently reaching 2.2 GPa; graphene membranes initially formed by filtration had a strength of 200 MPa, a record-breaking membrane strength of 1.55 GPa was recently achieved using static stretch-induced alignment technology. Existing technology annealing at very high temperatures (3000°C) can eliminate atomic defects on graphene sheets and promote the formation of graphite crystallites, resulting in a tensile strength of 3.4 GPa, graphene fiber with Young's modulus of 342 GPa. However, the use of high annealing temperatures is generally undesirable from an economic and ecological perspective, and the properties of the resulting macroscopic graphene are still much lower than those of single-layer graphene. Therefore, in order to replicate the excellent properties of graphene in macroscopic graphene fibers and films, it is of great interest to develop new strategies to prepare conductive graphene components with high mechanical properties, preferably at near room temperature.

technical problem

In the graphene fibers reported in the prior art, individual graphene sheets interact to form π-π connections in the overlapping direction, and the mechanical properties of the macrographene fibers thus formed need to be improved. The invention avoids fracture due to internal structural defects introduced when assembling 2D individual graphene sheets and achieves high tensile strength.

In the process of preparing graphene-based films, existing technology attempts to perform covalent bonding between graphene sheets, but these covalent bonds usually reduce conductivity due to the linking agent disrupting electron transport, and require functional modification to Restoring conductivity significantly increases preparation complexity. In order to solve the existing technical problems, the present invention discloses a simple graphene sheet assembly strategy to form a stable 2D connected planar structure, thereby significantly improving the mechanical and conductive properties.

Technical solutions

The present invention adopts the following technical solution: a graphene assembly fiber, using a graphene oxide aqueous solution as a spinning liquid, an amine compound aqueous solution as a coagulation bath, and obtaining a graphene assembly fiber through spinning and reduction treatment.

A graphene oxide fiber uses a graphene oxide aqueous solution as a spinning liquid and an amine compound aqueous solution as a coagulation bath. After spinning, the graphene oxide fiber is obtained.

In the present invention, the amine compound is an aromatic amine compound containing two or more amine groups; the chemical structural formula of the amine compound is R (NH ₂ ) _n , n is greater than 2, such as 2 to 8, preferably 2 to 6, and n represents There are n amine groups connected to R, which does not mean that n amine groups are repeated in series; R is an aryl group, a heterocyclic group, etc., and an aryl group includes a phenyl group, a substituted phenyl group, a biphenyl group, a substituted biphenyl group, and a fused ring Aromatic hydrocarbon group or substituted condensed ring aromatic hydrocarbon group, etc.; preferably, the molecular weight of the amine compound is less than 1000 and it is a small molecular compound.

In the present invention, a graphene oxide aqueous solution is injected into an amine compound aqueous solution to obtain graphene oxide fibers; and then the graphene oxide fibers are chemically reduced to obtain graphene assembly fibers. The method for preparing graphene oxide aqueous solution into graphene oxide fibers is a conventional method for preparing graphene oxide fibers. The creativity lies in the fact that the present invention uses an aqueous amine compound solution as a coagulation bath for the first time to obtain graphene oxide fibers. Preferably, the concentration of the graphene oxide aqueous solution is 0.1mg/mL~100mg/mL, preferably 1mg/mL~50mg/mL, and more preferably 2mg/mL~30mg/mL; the concentration of the amine compound aqueous solution is 0.1mM~30mM, preferably The range is 0.5mM to 20mM, more preferably 1mM to 10mM. As common sense, the amine compound can be prepared in the form of an amine compound salt, such as an amine compound hydrochloride or an amine compound sulfate.

In the present invention, the reducing agent for chemical reduction is hydriodic acid, hydrobromic acid, vitamin C, hydrazine hydrate, sodium hydroxide, sodium borohydride, etc. Chemical reduction is performed using reducing agent solution or reducing agent vapor. The temperature of chemical reduction is 50-150°C and the time is 30-200 minutes; the preferred temperature of chemical reduction is 70-120°C and the time is 60-150 minutes.

The invention discloses the application of amine compounds in preparing the above-mentioned graphene assembly fibers or graphene oxide fibers, and the amine compounds serve as flocculants. The invention improves the axial stress transfer between connected graphene sheets and the mechanical properties of the assembly. In particular, the conjugation of large-area graphene sheets can form an expanded π electron cloud, thereby achieving high electron mobility on the graphene sheets; Moreover, no foreign guest material is included between the stacked flakes, and results in a tight stacking of well-aligned graphene flakes, which favors π-π interactions and further improves mechanical and conductive properties. The invention discloses the application of the above-mentioned graphene assembly fiber or graphene oxide fiber in the preparation of functional fiber materials, or the application in the preparation of functional fiber composite materials. The so-called fiber composite materials refer to materials containing fibers or materials processed based on fibers through conventional methods. Conventional methods include weaving, spinning, bonding, etc. The so-called functions are electrical conductivity, thermal conductivity, antibacterial, flexibility, etc. For example, based on the graphene assembly fiber or graphene oxide fiber of the present invention, electrodes, conductive fibers, thermally conductive fibers, flexible sensing equipment, conductive graphene components, thermally conductive graphene components, electromagnetic shielding materials, graphene fiber cloth and Graphene fiber composite fabric, etc.

beneficial effects

The method of the present invention is simple and effective. It can be applied to high-performance fibers. The obtained graphene fibers show very high mechanical properties, with a tensile strength of 3.2±0.2 GPa and a Young’s modulus of 290±54 GPa, which is far from the This is higher than the best recorded values of 2.2 GPa and 183 GPa reported so far. Furthermore, the electrical conductivity measured along the fiber axis was 1.5 × 10 ⁵ S m ^-1 , which is an order of magnitude higher than the electrical conductivity of graphene fibers obtained in the prior art. Therefore, the method of assembling graphene of the present invention is expected to be used to produce macroscopic graphene assemblies with mechanical and electrical properties close to those of single graphene.

Description of the drawings

Figure 1 shows the characterization diagram of GO sheets.

Figure 2 is a schematic diagram of the preparation of graphene assembly fibers.

In Figure 3 (a) is the cross-sectional SEM image of the comparative graphene fiber sample, and (b) is the dark field TEM image.

Figure 4 is an optical microscope image of GO fibers spun from tubular channels of different diameters in the present invention.

Figure 5 is an optical microscope image of GO fibers spun from GO aqueous solutions of different concentrations in the present invention.

Figure 6 is an optical microscope image of the cross-section of a freshly solidified GO fiber.

Figure 7 shows that using a triangular nozzle, fibers with ribbon morphology can also be obtained.

Figure 8 is an SEM image of the GO fiber in Example 1, showing the smooth surface morphology and cross-section of the graphene fiber.

Figure 9 is an SEM image of the graphene assembly fiber of Example 1, showing a compact structure and good alignment in the stacking and longitudinal directions.

Figure 10 shows an example image of a fiber cross-section.

Figure 11 shows a dark field TEM image of fiber cross-section.

Figure 12 shows X-ray diffraction (XRD) and wide-angle X-ray scattering (WAXS) analysis.

Figure 13 shows the WAXS pattern (f) of graphene fiber, the radial (g) and azimuthal scan integration curve (h) of the WAXS mode.

Figure 14 shows the swelling behavior of GO fiber in water, where a is the fiber of Example 1 and b is the fiber of Comparative Example.

Figure 15 shows the solubility of graphene assembly fibers in acid.

Figure 16 shows the mechanical properties of graphene films. (a) Typical stress-strain curves of GO fibers and graphene assembly fibers; the dotted lines are copy data, (b) Raman spectra of graphene fibers under different external strains and (c) down-conversion of the Raman G band frequency with The relationship between external loading/unloading strain. Example SEM images show (d) the morphology of the fiber of Example 1 and (e) the fiber of the comparative example after fracture, and (f) the morphology of the fiber of the comparative example after fracture.

Figure 17 shows the mechanical properties test of graphene assembly fibers obtained from GO of different sizes.

Figure 18 shows the stress transmission of comparative graphene assembly fibers and control graphene assembly fibers.

Figure 19 is the stress-strain curve of the fiber before and after chemical reduction in Example 3.

Figure 20 shows the mechanical properties test of graphene assembly fibers obtained with different concentrations of 1,2,4,5-tetraaminobenzene hydrochloride aqueous solution.

Embodiments of the invention

In the present invention, the amine compound is an aromatic amine compound containing two or more amine groups; the chemical structural formula of the amine compound is R (NH ₂ ) _n , n is greater than 2, such as 2 to 8, preferably 2 to 6, and n represents There are n amine groups connected to R, which does not mean that n amine groups are repeated in series; R is an aryl group, a heterocyclic group, etc., and an aryl group includes a phenyl group, a substituted phenyl group, a biphenyl group, a substituted biphenyl group, and a fused ring Aromatic hydrocarbons and substituted condensed ring aromatic hydrocarbons, the substituents involved are halogens, alkyl groups, heteroatoms, etc.; preferably, the molecular weight of the amine compound is less than 1000, and it is a small molecular compound. As an example, the benzylamine compound of the present invention is one of the following: .

Among them, a is 1 to 10, preferably 1 to 5; the phenyl or substituted phenylamine compound is one of the following: .

Among them, R` is one or more of hydrogen, halogen, alkyl, alkoxy, heterocyclic group, and aromatic group, and the substitution position is not limited; b represents the number of amine groups, which is 2 to 4.

Examples of amine compounds include o-phenylenediamine, p-phenylenediamine, m-phenylenediamine, 3,4'-diaminodiphenyl ether, 1,2,4,5-tetraaminobenzene, 1,5-naphthylenediamine, 1,4-Naphthalenediamine, 4,4-diaminobiphenyl, 3,3',4,4'-biphenyltetramine, 2,3,5,6-pyridinetetramine, 2,2'-di Aminodiphenyl disulfide, 1,3-phenylenediamine, 4,4'-diaminodiphenylamine, 4,4'-diphenylbiphenyldiamine, 4,4'-diaminobenzoanilide, Meta-aminobenzylamine, 4,4`-diamino-2,2`-dimethyl-1,1`-biphenyl, 2,2`-diaminobiphenyl, 4,4'-diamino-3, 3'-dimethylbiphenyl, 3,3'-dichlorobenzidine, 3,3',5,5'-tetramethylbenzidine, 3,3'-diaminobenzidine, 3,3'- Diaminobenzidine (1,1'-biphenyl)-3,3'4,4'-tetraamine, 4,4''-diaminotetrabiphenyl, anthraquinone-1,8-diamine, 1 ,5-diaminoanthraquinone, 2,6-diaminoanthraquinone, 1,2-diaminoanthraquinone, 1,4-diaminoanthraquinone, 1,-diamino-9,10-anthracenedione, 1 ,4,5,8-tetraaminoanthraquinone, 5,6-diamino-1,10-phenanthroline, 3,8-diamino-6-phenylphenanthridine.

As common sense, amine compounds can be prepared in the form of amine compound salts. The solution concentration is based on the amine compound; amine compound hydrochloride or amine compound sulfate can be selected, such as 3,3'-diaminobenzidine hydrochloride. (1,1'-Biphenyl)-3,3'4,4'-tetraaminetetrahydrochloride (CAS No.:868272-85-9), 1,2,4,5-tetraaminobenzene hydrochloride salt, ethylenediamine hydrochloride, p-phenylenediamine hydrochloride, naphthalenediamine hydrochloride, benzidine hydrochloride, etc.

As an example: the present invention adopts an industrially applicable wet spinning scheme, in which aqueous GO is injected with an aromatic amine solution used as a flocculant; the solidified GO is then chemically reduced to prepare graphene fibers. Specifically, the present invention prefers aromatic amines as flocculants, and their aromatic rings are connected to -NH ₂ substituents to achieve rapid solidification of GO sheets; then chemical reduction forms a graphene structure. The graphene oxide aqueous solution can be injected into the coagulation bath through a spinning tube. The inner diameter of the spinning tube can be 1 μm to 1 cm. The specific injection method is a conventional technology in which the graphene oxide aqueous solution is assembled into fibers.

Expandable graphite (approximately 300 μm) was purchased from Nanjing Pioneer Nanomaterial Technology Co., Ltd.; hydrochloric acid (HCl, 12 mol L ^-1 ), potassium permanganate (KMnO ₄ , ≥99.5%) and sulfuric acid (H ₂ SO ₄ , 98% ) was purchased from Jiangsu Johnson & Johnson Functional Chemical Co., Ltd.; hydrogen peroxide (H ₂ O ₂ , 30%) was purchased from Shanghai Lingfeng Chemical Reagent Co., Ltd.; hydroiodic acid (HI, 57 wt%) was purchased from Adamas Beta; 1,2 ,4,5-tetraaminobenzene hydrochloride was obtained from Shanghai Bidepharmatech Co., Ltd., with the following structural formula: .

The tensile strength test was performed using a commercial mechanical tensile testing system (HY-0350, Shanghai Hengyi Precision Instrument Co., Ltd.) equipped with a precision force detector program with an accuracy of 0.00001 N. The individual fibers were glued to a rectangular paper frame and mounted to the test system. The specified tensile test length is 5 to 20 mm, and different loading strain rates include 0.01, 0.05, and 0.1 mm min ^-1 . Adjusting the above parameters has no significant impact on mechanical property measurements.

Conductivity (σ) was measured using the standard four-probe method. Attach four equally spaced collinear silver probes to the same side of the fiber sample using silver paste. A Keithley2400 multifunctional instrument is used as the current source, current is applied to the probes at both ends, and the corresponding voltage changes of the two inner probes are measured. σ (S m ^-1 ) is calculated according to the following formula: .

where I (A) is the applied current, U (V) is the corresponding voltage, S (m ² ) is the cross-sectional area measured by SEM, and L (m) is the distance between electrodes (10 mm).

The raw materials used in the present invention are all commercially available products, and the specific preparation operations and testing methods are conventional techniques.

Synthesis example: GO nanosheets are prepared according to the existing modified Hummers method. 1g of expandable graphite is maintained at 1000°C for 30 seconds, then added to 60ml of sulfuric acid, heated to 80°C, and then 0.84g of potassium persulfate and 1.24g of pentoxide are added. diphosphorus, then add 40ml sulfuric acid and 3g potassium permanganate for oxidation, and then add 2ml hydrogen peroxide. After the reaction, the product is separated, and then washed with hydrochloric acid and water to obtain graphene oxide (GO) dispersed in water. The base and edges of GO sheets are rich in polar oxygen-containing functional groups, which lead to negative surface charges and form stable aqueous dispersions. The oxygen-containing functional groups are usually hydroxyl groups (C–OH), epoxy groups (C– O–C) and carboxyl (–C(=O)OH). Figure 1 shows the characterization diagram of GO sheets. Atomic force microscopy (AFM) and scanning electron microscopy (SEM) show that the lateral size of GO sheets is mainly between 10-70 μm, and the average thickness is about 1 nm; using X-ray photoelectron spectroscopy (XPS) ) and Fourier transform infrared spectroscopy (FTIR) verified the presence of oxygen-containing groups, and elemental analysis showed that the C:O atomic ratio was 1.15.

Example 1 Preparation of graphene assembly fibers: GO aqueous solution (10 mg/mL) is squeezed into 1,2,4,5-tetraaminobenzene hydrochloride aqueous solution (5mM) through a syringe (inner diameter: 160 μm), and a gel is visible Fibers are formed, and then brown-yellow GO fibers are formed after rotating in the coagulation bath for 5 minutes. The GO fibers are picked out and collected. See Figure 2. A watch glass containing 1,2,4,5-tetraaminobenzene hydrochloride aqueous solution is placed in the Rotate on the rotating table; use glass rods to pick out and collect the fibers; then suspend the GO fibers on parallel rods and expose them to hydriodic acid vapor at 90°C for 12 hours; then wash them 5 times with water and ethanol alternately to remove iodine ions, etc., to obtain graphene assembly fibers. Conventional testing showed no iodine residue, and the weight density was 1.90 g cm ^-3 , measured using the float-sink method.

Example 2: Based on Example 1, the inner diameter of the syringe is 1.5 mm, 500 μm or 340 μm, and the rest is the same to obtain graphene assembly fibers.

On the basis of Example 1, the concentration of the GO aqueous solution is 1 mg/mL or 20 mg/mL, and the rest is the same to obtain graphene assembly fibers.

Comparative Example: GO was dispersed in DMF, ethyl acetate was used as the coagulation bath, and other conditions were the same as Example 1 to obtain comparative graphene assembly fibers.

Comparative example: Calcium chloride in ethanol/water (1:3 v/v) solution (5wt%) was used as the coagulation bath instead of the 1,2,4,5-tetraaminobenzene hydrochloride aqueous solution in Example 1. Other conditions Without changing, the control graphene assembly fiber was obtained.

Analysis of results: Generally, solvent exchange between GO dispersed in dimethylformamide and the common coagulant ethyl acetate limits the geometry of the channels, and therefore, as confirmed by morphological and microstructural characteristics, the tubular channels are generally is to produce fibers with circular cross-sections and maintain the random arrangement of the aqueous dispersion. In Figure 3 (a) is the cross-sectional SEM image of the comparative graphene fiber sample, (b) is its dark field TEM image, it can be seen , the circular geometry of the nozzle and the random flake orientation in the starting aqueous dispersion remain unchanged after solidification.

Although the nozzle is circular, the graphene assembly fibers formed in the embodiments of the present invention have an unusual ribbon morphology. The unique edge assembly can spontaneously generate a ribbon morphology with an ordered assembly, which can enhance the relationship between the graphene planes. The π-π interaction leads to its self-assembly into anisotropic ribbon morphology. Figure 4 is an optical microscope image of GO fibers spun from tubular channels of different diameters. Figure 5 is an optical microscope image of GO fibers spun from GO aqueous solutions with different concentrations. In all cases, the fibers exhibit a ribbon-like morphology.

For tubular channels with an inner diameter up to 1500 μm, the optical microscope image of the cross-section of the freshly solidified GO fiber is shown in Figure 6, showing an immediate flattening into a ribbon shape. Even with a triangular nozzle, fibers with ribbon-like morphology can be obtained (Fig. 7). According to the prior art, the shear stress gradient along the transverse direction of the nozzle during wet spinning usually results in skin effect or uneven core-sheath structure in the fiber, but the present invention unexpectedly results in ribbon-like fibers, as shown in the transverse image. The compactness across the entire cross-section is high and there are no gaps (Figure 8), which is significantly different from the disordered arrangement of micropores between the graphene sheets of the prior art. The highly aligned structure of GO fibers remained well maintained during the reduction step (Fig. 9).

Atomic-level information of graphene assembly fibers was obtained through transmission electron microscopy (TEM). Figure 10 shows an example image of a fiber cross-section, confirming the presence of a large area of graphite lattice, almost perfectly aligned. The corresponding selected area electron diffraction (SAED) pattern in the inset shows only 00l spots, which are sharp and straight, with The distance is 0.336 nm, close to the stacking distance in an ideal graphite structure, small values of interlayer distance indicate few structural defects, including flake wrinkling, stacking faults, or the presence of guest molecules between stacked flakes. Studies of longitudinal flakes also show that the graphene sheets are uniformly aligned along the fiber axis with a coherence length (Laxis) greater than several hundred nanometers (Figure 11). X-ray diffraction (XRD) and wide-angle X-ray scattering (WAXS) analyzes were performed to provide complementary information on the fiber structure. The repeating distances between closely stacked graphene sheets estimated from XRD data are generally consistent with those measured by TEM (Fig. 12). In the two-dimensional WAXS map, the signals corresponding to the graphite structures (002) and (100) are clearly observed (Fig. 13, f–g), with the half-peak width of the (002) azimuthal intensity distribution (expressed as the orientation angle, (usually a measure of the degree of texture) is as small as 19.4° (h in Figure 13), indicating a highly preferentially ordered structure aligned along the graphene plane, with a corresponding orientation factor (f) as high as 0.896. Therefore, all data confirm that the ribbon-like graphene assembly fibers of the present invention are composed of regular and closely stacked planar graphene sheets, which are very similar to the ideal graphite structure.

By studying the swelling behavior of GO fibers in water, strong connectivity between the assembled sheets can be observed. Due to the hydrophilicity of the oxygen-containing groups on the surface, the GO fibers in the comparison experiment would expand indefinitely and decompose quickly. On the contrary, the GO fiber of Example 1 maintained good structural integrity (Figure 14). In addition, the graphene assembly fiber of Example 1 was maintained in the strong acid of 12 M HCl for 1 hour, and the structure of the fiber was intact. The subsequent strong ultrasonic treatment did not even destroy the integrity of the fiber. In contrast, the fiber of the comparative example decomposes in a few minutes in 1 M dilute HCl, see Figure 15, where (a) Example 1 graphene assembly fiber is in 12 M HCl for 1 hour, (b) Example 1 graphene assembly Changes in body fiber (I), Example 3 (ethylenediamine hydrochloride) graphene fiber (II), and control example (Ca ²⁺ ) graphene assembly fiber (III) immersed in 1 M HCl, (II ), (III) completely dissolved in 5 minutes.

While single-sheet graphene is one of the strongest materials known, with excellent tensile strength and Young's modulus, the mechanical tensile behavior of macroscopic fibers composed of assembled graphene sheets depends primarily on inter-sheet interactions , especially the interaction along the fiber axis, which causes the mechanical properties of the graphene assembly to be improved. Taking the product of Embodiment 1 as an example, it is shown that the present invention improves the mechanical properties of the graphene assembly. Figure 16 a shows the tensile stress curve of GO fiber and graphene assembly fiber (length 10 mm). The tensile strength of the GO fiber is 1.9±0.09 GPa (the highest value reported so far), and the Young's modulus when the breaking strain is 1.3±0.3% is 153±41 GPa; the tensile strength of the graphene assembly fiber increases to 3.2 ±0.2 GPa, Young's modulus is 290±54 GPa, and breaking strain is 1.1±0.2%; compared with the highest reported value (2.25 GPa) of graphene fibers prepared by the existing technology, the mechanical strength of the fiber of the present invention is high Out 1.42 times. In particular, the strength value of the present invention is comparable to the strength value of graphene fibers graphitized at extremely high temperatures (3.40 GPa) and 1.7 times that of graphitized annealed graphene fibers obtained by microfluidic assembly (1.90 GPa). The significant enhancement in mechanical strength is due to the optimization of inter-chip connections at the atomic scale and the compact stacking at the microscopic scale. Similarly, the Young's modulus of the fiber of the present invention is also significantly higher than other graphene fibers prepared at near room temperature, and is close to the Young's modulus of the fiber after high-temperature graphitization treatment. It is generally believed that high-temperature graphitization to form a highly ordered lattice is crucial to obtain high Young's modulus, but in the present invention, at such a low preparation temperature (room temperature), the high Young's modulus means that it is almost essentially The defective graphene structure is orderly stacked on the atomic or lattice scale and enhances π-π interactions. Table 1 details the performance indicators of the graphene fiber of the present invention and the values reported in the literature. The mechanical properties of macroscopic fiber assemblies are highly dependent on the stress transfer mechanism between individual graphene sheets. Raman spectroscopy is a useful tool for quantitatively observing this effect by measuring the displacement of characteristic bands under strain, as shown in the Raman spectroscopy (bc in Figure 16) where graphene G bands are observed due to tensile strain on the individual flakes redshift. For comparison, the increase in stress transfer in the control graphene assembly fiber only occurs at low strain values (Fig. 18). The cross-sectional morphology of the fracture surface also confirmed this difference. After continuous sliding fracture, the fiber surface of the invention was smoother than that of the control sample (df in Figure 16). The graphene assembly fiber of the present invention shows a higher Raman shift strain dependence: 9.54 cm ^-1 /%, the comparative example is 6.57 cm ^-1 /%, and the comparative example is 5.89 cm ^-1 /%.

On the basis of Example 1, large-sized or small-sized GO is selected. In the same method, graphene assembly fibers are obtained. The mechanical properties test is shown in Figure 17, where (a) is the AFM image and size distribution of GO with different lateral sizes. And (b) the tensile strength of the graphene assembly fiber; the graphene oxide aqueous solution in the synthesis example was size screened by centrifugation: centrifuge at 4000 rpm for 5 minutes and then remove the layer to obtain >40 μm large size GO, and then centrifuge at 6000 rpm for 5 minutes Then take the upper layer to obtain <30μm small size GO; adjust the concentration routinely.

Table 1 Mechanical strength of the graphene assembly fiber of the present invention and existing fibers.

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The electrical conductivity of graphene-based materials is seriously affected by structural defects. In addition to improving mechanical strength, the fiber of the present invention also improves electronic conduction, thereby increasing the overall electronic conductivity, with 1.5 (±0.02) × 10 ⁵ S m ⁻¹ The excellent electrical conductivity is an order of magnitude higher than the electrical conductivity of graphene fibers prepared at low temperatures using the existing technology (Table 2).

Table 2 Electrical conductivity of graphene assembly fibers of the present invention and existing fibers.

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Graphene has excellent mechanical and electrical properties. These excellent properties originate from its unique hexagonal lattice composed of carbon atoms. Each carbon atom is connected to three other carbon atoms. The carbon atoms in this unit pass through strong coherence. Valence σ bonds, formed by overlapping sp ^hybrid orbitals, contribute to graphene's high electrical conductivity. Because graphene's single-atom thickness and large area give it a large aspect ratio, graphene sheets can be assembled into macroscopic structures such as graphene fibers. The starting point for the synthesis of macroscopic graphene is usually graphite oxide dispersed in a solvent. ene (GO), fibers are made from dispersed GO through wet spinning technology, and then graphene-based fibers are obtained through chemical or thermal reduction.

The prior art emphasizes the importance of reducing structural defects and improving the regular arrangement of graphene sheets to enhance the mechanical and electrical properties of graphene fibers. High-temperature annealing can eliminate atomic defects on graphene sheets and promote the formation of graphite crystallites, resulting in a tensile strength of 3.4 GPa, graphene fiber with Young's modulus of 342 GPa. However, the use of high annealing temperatures is generally undesirable from an economic and ecological perspective, and the properties of the resulting macroscopic graphene are still much lower than expected from a single graphene layer. Therefore, it is particularly important to develop new strategies to prepare macroscopic graphene fibers at near room temperature and further prepare conductive graphene components with high mechanical properties.

Example 3: GO aqueous solution (10mg/mL) was extruded into ethylenediamine hydrochloride aqueous solution (5mM) through a syringe (inner diameter 160μm). It can be seen that gel fibers were formed, and then brown-yellow GO was formed after rotating in the coagulation bath for 5 minutes. fibers, pick out and collect GO fibers.

The GO aqueous solution (10mg/mL) was extruded into the octanediamine aqueous solution (5mM) through a syringe (inner diameter 160μm). It can be seen that gel fibers were formed, and then brown GO fibers were formed after rotating in the coagulation bath for 5 minutes. Pick out and collect the GO fiber.

The GO aqueous solution (10mg/mL) was extruded into the p-phenylenediamine hydrochloride aqueous solution (5mM) through a syringe (inner diameter 160μm). It can be seen that gel fibers were formed, and then brown-yellow GO fibers were formed after rotating in the coagulation bath for 5 minutes. Take out and collect the GO fibers.

The GO aqueous solution (10mg/mL) was extruded into the naphthalenediamine hydrochloride aqueous solution (5mM) through a syringe (inner diameter 160μm). It can be seen that gel fibers were formed, and then after rotating in the coagulation bath for 5 minutes, brown-yellow GO fibers were formed and picked out. and collect GO fibers.

The GO aqueous solution (10mg/mL) was extruded into the 4,4-diaminobiphenyl hydrochloride aqueous solution (5mM) through a syringe (inner diameter 160μm). It can be seen that gel fibers were formed, and then a brownish yellow color was formed after rotating in the coagulation bath for 5 minutes. GO fibers, pick out and collect GO fibers.

The above-mentioned GO fibers were suspended on parallel rods and exposed to hydriodic acid vapor at 90°C for 12 hours; then washed 5 times with water and ethanol alternately to remove iodide ions, etc., to obtain graphene assembly fibers. There was no iodine residue in conventional tests. The mechanical property test is shown in Figure 19, which is the stress-strain curve of the fiber before and after chemical reduction; the tensile strength and electrical conductivity of graphene fibers obtained with different coagulants are shown in Table 3.

Table 3 Tensile strength and electrical conductivity of graphene fibers obtained with different coagulants.

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The graphene fibers obtained from aromatic amines have a ribbon-like geometric shape different from that of the nozzle, exhibiting the same phenomenon as Example 1. The remaining graphene fibers have a circular geometric shape of the nozzle.

Example 4: GO aqueous solution (10mg/mL) is squeezed into 1,2,4,5-tetraaminophenyl hydrochloride aqueous solution (2.5 or 10mM) through a syringe (inner diameter 160μm). It can be seen that gel fibers are formed and then solidified. Brown GO fibers were formed after rotating in the bath for 5 minutes. Pick out and collect the GO fibers; use a glass rod to pick out and collect the fibers; then suspend the GO fibers on parallel rods and expose them to hydriodic acid vapor at 90°C for 12 hours; then wash 5 times with water and ethanol alternately to remove iodide ions, etc., and obtain the graphene assembly fiber. There is no iodine residue in the conventional test. The mechanical property test is shown in Figure 20, which is the stress-strain curve of the fiber after chemical reduction.

Example 5: GO aqueous solution (10mg/mL) is extruded into 1,2,4,5-tetraaminobenzene hydrochloride aqueous solution (5mM) through a syringe (inner diameter 160μm). It can be seen that gel fibers are formed, and then in the coagulation bath After rotating for 5 minutes, brown GO fibers are formed. Pick out and collect the GO fibers with a glass rod; then suspend the GO fibers on the parallel rods and expose them to hydriodic acid vapor at 90°C for 6 or 9 hours. ; Then wash it alternately 5 times with water and ethanol to remove iodide ions, etc., and obtain the graphene assembly fiber. According to conventional tests, there is no iodine residue, the tensile strength is about 3 GPa, and the electrical conductivity is on the order of 10 ⁵ S m ^-1 .

Example 6: GO aqueous solution (10mg/mL) is extruded into 3,3'-diaminobenzidine hydrochloride aqueous solution (5mM) through a syringe (inner diameter 160μm). It can be seen that gel fibers are formed, and then rotated in the coagulation bath After 5 minutes, GO fibers were formed, and the GO fibers were picked out and collected; then the GO fibers were suspended on parallel rods and exposed to hydriodic acid vapor at 90°C for 8 hours; then washed 5 times alternately with water and ethanol to remove iodide ions, etc. , obtaining graphene assembly fibers.

For the first time, this invention uses an aromatic amine compound as a coagulation bath to obtain graphene oxide fibers at room temperature under conventional wet spinning processes, and then chemically reduces them into graphene assembly fibers to avoid the introduction of 2D single graphene sheets when assembling them. Fracture occurs due to internal structural defects, and high tensile strength is achieved under the interaction between the edge of the sheet and the in-plane sheet, overcoming the problem of the upper limit bottleneck of the mechanical properties of existing graphene assembly fibers, especially avoiding the existing technology to improve There is a problem of reducing conductive properties due to mechanical properties, because covalent bonding between prior art graphene sheets often reduces conductivity due to interruption of electron transport by the linker, and requires functional modification to restore it. In the present invention, the axial stress transmission between connected graphene sheets and the mechanical properties of the components are improved. The conjugation of large-area graphene sheets can form an extended electron cloud covering the entire connection plane, thereby achieving high electron density on the graphene sheets. mobility, and avoids the entrapment of foreign guest molecules between stacked flakes and forms a compact stack of well-aligned graphene flakes, further improving mechanical and electrical properties. The method of the present invention is simple and effective, and it can be applied to high-performance fibers and films. The graphene fiber obtained by the method of the present invention has very high mechanical properties, with a tensile strength of 3.2±0.2 GPa and a Young's modulus of 290±54 GPa. This is much higher than the best recorded values of 2.2 GPa and 183 GPa reported to date. Furthermore, the electrical conductivity measured along the fiber axis was 1.5 × 10 ⁵ S m ^-1 , which is an order of magnitude higher than that of graphene fibers obtained at similar temperatures.

In summary, we develop a new strategy to obtain macroscopic graphene structures with high strength and modulus as well as excellent electronic conductivity at near room temperature. In the present invention, the connected larger graphene sheets are highly oriented and tightly stacked, and the edge connections and accompanying extended conjugated structure improve the mechanical properties and electronic conductivity of the fiber, especially without the need for high-temperature annealing. The method of the present invention is simple and effective, and can be applied to the manufacture of macroscopic fibers. The fibers produced at near room temperature are simultaneously enhanced in terms of tensile strength, modulus and electrical conductivity, which highlights the use of graphene as a precursor to carbon fiber manufacturing in the present invention. The advantages of the polymer are significantly better than traditional pyrolysis methods to prepare polyacrylonitrile (PAN) and mesophase pitch (MPP)-based fibers. In addition, this work introduces a new method to design high-performance macroscopic graphene assemblies, which may be interesting for further research on other 2D material assemblies and commercial industrial applications related to high-performance structural materials.

Claims

A graphene assembly fiber, which is characterized in that a graphene oxide aqueous solution is used as a spinning liquid, an amine compound aqueous solution is used as a coagulation bath, and a graphene assembly fiber is obtained through spinning and reduction treatment; the amine compound is composed of two or more Aromatic amine compounds with more than amine groups.
A kind of graphene oxide fiber, characterized in that, graphene oxide aqueous solution is used as the spinning liquid, and the amine compound aqueous solution is used as the coagulation bath. After spinning, the graphene oxide fiber is obtained; the amine compound contains two or more amine groups. of aromatic amine compounds.
The fiber according to claim 1 or 2, characterized in that the chemical structural formula of the amine compound is R (NH 2 ) n , n is greater than 2, and n represents n amine groups connected to R; R is an aryl group, a hetero group, Ring group; the molecular weight of amine compounds is less than 1000.
The fiber according to claim 3, wherein the aryl group includes a phenyl group, a substituted phenyl group, a biphenyl group, a substituted biphenyl group, a condensed ring aromatic hydrocarbon group or a substituted condensed ring aromatic hydrocarbon group.
The preparation method of graphene assembly fiber according to claim 1, characterized in that the graphene oxide aqueous solution is injected into the amine compound aqueous solution to obtain the graphene oxide fiber; and then the graphene oxide fiber is chemically reduced to obtain the graphene assembly. fiber.
The method for preparing graphene assembly fiber according to claim 5, characterized in that the concentration of the graphene oxide aqueous solution is 0.1 mg/mL~100 mg/mL; the concentration of the amine compound aqueous solution is 0.1mM~30mM.
The method for preparing graphene assembly fibers according to claim 5, wherein the reducing agent for chemical reduction includes hydriodic acid, vitamin C, hydrazine hydrate, sodium hydroxide or sodium borohydride.
The application of amine compounds in preparing the graphene assembly fiber of claim 1 or the graphene oxide fiber of claim 2 is characterized in that the amine compound is a compound containing two or more amine groups.
The application of the graphene assembly fiber of claim 1 or the graphene oxide fiber of claim 2 in the preparation of functional fiber materials, or the application in the preparation of functional fiber composite materials.
The graphene assembly fiber of claim 1 is used in the preparation of graphene fiber capacitors, graphene fiber electrodes, graphene fiber fabrics, conductive fibers, thermally conductive fibers, flexible sensing equipment, conductive graphene components, thermally conductive graphene components, and electromagnetic shielding. Applications in Materials.