A self-twisted high thermal conductivity flexible graphene fiber and preparation method thereof

Abstract

The present invention discloses a self-twisting, highly thermally conductive, flexible graphene fiber and its preparation method. Water is added to an organic-phase graphite oxide spinning solution. During the coagulation and drying process of the gel fiber, both an organic phase and an aqueous phase coexist within the fiber. The uneven evaporation rate of the two-phase solvent leads to solvent concentration gradients and surface tension gradients on the fiber surface. This unevenness induces the Marangoni effect and causes the gel fiber to undergo rotational self-twist. This method allows for controllable adjustment of fiber twist by adjusting the water content of the initial spinning solution. The self-twisted fiber is then chemically reduced and graphitized to produce a highly thermally conductive, flexible graphene fiber.

Description

Technical Field

[0001] The present invention relates to the field of graphene fiber preparation, and in particular to a self-twisted high-thermal-conductivity flexible graphene fiber and a preparation method thereof. Background Art

[0002] Graphene's extremely high electrical conductivity, far exceeding that of traditional conductors like copper, makes it an ideal material for next-generation electronic devices and high-efficiency batteries. Graphene also has excellent thermal conductivity, effectively dissipating heat, making it an excellent material for heat dissipation and thermal management. Furthermore, graphene possesses exceptional mechanical strength, with tensile strength hundreds of times greater than that of steel, yet is remarkably lightweight, making it valuable for applications in lightweight materials and structural reinforcement.

[0003] Graphene fiber, a new type of fiber made from graphene, combines the excellent properties of graphene with the flexibility of fiber. Due to its unique two-dimensional structure, graphene fiber has extremely high electrical and thermal conductivity and mechanical strength, and can withstand enormous tensile and bending loads while remaining lightweight. These properties give graphene fiber broad application potential in multiple fields, especially in flexible electronics and sensors. However, the current elongation at break of graphene fiber is below 1%, making it a brittle material. Its excellent electrical and thermal conductivity properties make it difficult to apply in flexible applications. Although some existing twisting techniques can improve the elongation at break of graphene fiber to a certain extent, the subsequent twisting introduces a defect that significantly reduces the fiber's strength, failing to meet the basic fiber strength requirements for weaving. This seriously hinders the application and development of graphene fiber in flexible, high-thermal conductivity and electronics fields. Summary of the Invention

[0004] The present invention addresses the defects of the prior art that the method for preparing twisted graphene fibers requires a complicated post-twisting device and the significantly reduced strength of the prepared twisted graphene fibers. The present invention provides a self-twisting high-thermal-conductivity flexible graphene fiber and a preparation method thereof.

[0005] The present invention introduces a second-phase solvent, water, into a single-phase graphene oxide dispersion. During the drying process, the uneven volatilization of the two-phase solvent caused by the Magrani effect causes the fibers to self-twist, thereby efficiently and quickly preparing self-twisting graphene oxide fibers. Subsequently, through a subsequent chemical reduction and graphitization process, high-strength, high-breaking elongation, high thermal conductivity, and flexible graphene fibers with adjustable twisting degree are obtained.

[0006] One of the technical solutions of the present invention is to provide a method for preparing a self-twisted high thermal conductivity flexible graphene fiber, which is characterized by comprising the following steps:

[0007] (1) adding water as a second phase to an organic phase graphene oxide dispersion and mixing them uniformly to obtain a graphene oxide two-phase spinning solution; the water accounts for 1% to 15% of the total solvent volume;

[0008] (2) The graphene oxide two-phase spinning solution is squeezed into the coagulation bath through the spinning head through the extended spinning head. The graphene oxide sheets are sheared by the tube wall in the extended spinning head to achieve high axial orientation. After sufficient coagulation, the graphene oxide gel fiber containing the two-phase solvent is obtained. The fiber is then pulled out for drying and continuously collected on a roller. During the drying process, the unstable volatilization caused by the difference in surface tension of the two-phase solvent produces the Marangoni effect, which causes the fiber to self-twist, thus obtaining a self-twisting graphene oxide fiber.

[0009] (3) sending the dried self-twisted graphene oxide fibers into a reduction bath for continuous in-situ chemical reduction, and collecting the self-twisted reduced graphene oxide fibers;

[0010] (4) The reduced graphene oxide fibers are graphitized in a high-temperature inert gas atmosphere to obtain self-twisted graphene fibers.

[0011] Furthermore, the solvent of the organic phase graphene oxide dispersion described in step 1 is one of N,N-dimethylformamide, N,N-dimethylacetamide, tetrahydrofuran, dimethyl sulfoxide, N-methylpyrrolidone, ethylene glycol, diethylene glycol, and pyridine.

[0012] Furthermore, the concentration of the graphene oxide dual-phase spinning solution is 3 mg / g-20 mg / g.

[0013] Furthermore, the length of the extended spinning head in step 2 is 1 cm to 5 cm.

[0014] Furthermore, the coagulation bath in step 2 is an organic solvent that is immiscible with water, including one or more of ethyl acetate, dichloromethane, n-hexane, cyclohexane, toluene, n-butanol, carbon tetrachloride, benzene, chloroform, cyclopentane, dichloroethane, ether, n-heptane, methyl ethyl ketone, isooctane, pentane, dipropyl alcohol, tetrachloroethane, trichloroethane, and xylene.

[0015] Furthermore, the reducing bath in step 3 comprises one or more of acetic acid, trifluoroacetic acid, vitamin C, hydroiodic acid, and hydrazine hydrate.

[0016] Furthermore, the graphitization process in step 4 is to first perform a carbonization treatment at 1000°C-1200°C and then a graphitization treatment at 3000°C under the protection of an inert gas.

[0017] The second technical solution of the present invention is to provide a self-twisted high thermal conductivity flexible graphene fiber prepared by the above preparation method.

[0018] The fiber wrinkles are oriented radially and gradually transition to the axial direction during stretching, resulting in a high elongation at break. In the extended spinning head, the shear force from the tube wall causes the lamellae to align neatly along the fiber axis. During the subsequent spiraling process, the fiber lamellae remain neatly aligned in the spiral direction. This orderly stacking of lamellae ensures that the fiber maintains high strength while achieving high elongation at break.

[0019] Beneficial effects of the present invention:

[0020] (1) By introducing the aqueous phase into the organic phase spinning solution system and cleverly utilizing the difference in surface tension and volatilization rate of the two phase solvents, the Marangoni effect is generated, which drives the self-twisting phenomenon of the macro gel fiber. This is a new method and system for preparing self-twisting fibers.

[0021] (2) The spiral process occurs spontaneously during the drying process, without the need for additional subsequent twisting devices, and can achieve precise adjustment of the fiber spirality, greatly improving the production efficiency and flexibility of the fiber.

[0022] (3) Compared with the subsequent additional twisting method, the large gaps and defects introduced by twisting after the fiber is fully dried are avoided.

[0023] (4) By using an extended spinning head, the sheet is fully oriented along the fiber axis under the action of the shear force of the inner tube wall of the spinning head, so that the obtained fiber has high breaking strength while maintaining high breaking elongation. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 Flow chart of preparation of Marangoni self-twisted fibers;

[0025] Figure 2 Digital camera photos of the self-twisting areas of gel fibers with different water contents;

[0026] Figure 3 SEM photo of microscopic spiral wrinkles of high thermal conductivity flexible fiber;

[0027] Figure 4 Elongation at break of fibers with different water contents (after heat treatment at 3000°C);

[0028] Figure 5 Thermal conductivity of fibers with different water contents (after heat treatment at 3000°C);

[0029] Figure 6 Electrical conductivity of fibers with different water contents (after heat treatment at 3000℃). DETAILED DESCRIPTION

[0030] The following examples are used to further illustrate the present invention. Their purpose is to illustrate the present invention and should not be construed as limiting the scope of the present invention. Unless otherwise specified, all references are by weight and weight percentage.

[0031] Unless otherwise specified, the raw materials used in the present invention are conventional commercial products; the methods used in the present invention are conventional methods in the art unless otherwise specified.

[0032] The embodiments of the present invention are further described below with reference to a number of embodiments.

[0033] It should be clear that the embodiments described are only part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0034] The terms used in the embodiments of the present application are only for the purpose of describing specific embodiments and are not intended to limit the present application. The singular forms "a", "an", "the" and "the" used in the embodiments of the present application and the appended claims are also intended to include plural forms unless the context clearly indicates otherwise. Example 1

[0035] (1) Prepare a graphene oxide dispersion with a concentration of 3 mg / g and a solvent of N,N-dimethylformamide;

[0036] Deionized water was added to the dispersion and mixed evenly to obtain a GO biphasic spinning solution with a second phase water content of 5%;

[0037] (2) The above-mentioned two-phase spinning solution is loaded into a degassing device and a syringe. A needle with a length of 1 cm and a diameter of 130 μm is used as a spinning head. The spinning solution is squeezed into an ethyl acetate coagulation bath. After sufficient coagulation, a gel fiber containing two-phase components of ethyl acetate and the second phase solvent water is obtained;

[0038] (3) The gel fiber is pulled out of the coagulation bath and dried. During the drying process, the two-phase volatilization of ethyl acetate and water causes the Magranie effect to occur, driving the fiber to twist, such as Figure 2 As shown in the figure, the camera photos show that the drying fibers show light and dark changes under the light due to their spiral structure;

[0039] (4) The self-twisted graphene oxide fibers are continuously collected and sent into a chemical reduction bath for continuous chemical reduction to obtain reduced graphene oxide fibers.

[0040] (5) The reduced graphene oxide was placed in an inert gas argon atmosphere and carbonized at 1200℃ and then graphitized at 3000℃ to obtain high thermal conductivity flexible graphene fiber. The elongation at break was 25%, the strength was 1.23GPa, and the conductivity was 0.89×10 6 S / m, thermal conductivity is 966W / m K. Example 2

[0041] (1) A graphene oxide dispersion with a concentration of 8 mg / g and a solvent of dimethyl sulfoxide was prepared; deionized water with a mass fraction of 5% was added to the dispersion and mixed evenly to obtain a GO two-phase spinning solution with a second phase water content of 5%;

[0042] (2) The above-mentioned two-phase spinning solution is loaded into a degassing device and loaded into a syringe. A needle with a length of 5 cm and a diameter of 130 μm is used as a spinning head. The spinning solution is squeezed into a n-hexane coagulation bath. After sufficient coagulation, a gel fiber containing a two-phase component of n-hexane and a second phase solvent of water is obtained;

[0043] (3) The gel fiber is pulled out of the coagulation bath and dried. During the drying process, the two-phase volatilization of ethyl acetate and water causes the Magranie effect to occur, driving the fiber to twist, such as Figure 2 As shown in the figure, the camera photos show that the drying fibers show light and dark changes under the light due to their spiral structure;

[0044] (4) The self-twisted graphene oxide fibers are continuously collected and sent into a chemical reduction bath for continuous chemical reduction to obtain reduced graphene oxide fibers.

[0045] (5) The reduced graphene oxide was placed in an inert gas argon atmosphere and subjected to carbonization treatment at 1000°C and then graphitization heat treatment at 3000°C to obtain high thermal conductivity flexible graphene fiber. The elongation at break was 24%. The strength was 1.32 GPa and the conductivity was 0.9×10 6 S / m, thermal conductivity is 987W / m K. Example 3

[0046] This comparative example is the same as Example 1, except that the concentration of the graphene oxide dispersion is 20 mg / g and the proportion of the second phase water is 1%.

[0047] The graphene fiber obtained has a breaking elongation of 20%, a strength of 1.35 GPa, and a conductivity of 0.97×10 6 S / m, thermal conductivity is 1012W / m K. Example 4

[0048] This comparative example is the same as Example 1, except that the proportion of the second phase water is 15%.

[0049] The graphene fiber obtained has a breaking elongation of 32%, a strength of 1.02 GPa, and a conductivity of 0.86×10 6 S / m, thermal conductivity is 921W / m K

[0050] Comparative Example 1

[0051] This comparative example is the same as Example 1, except that the second phase solvent water is not introduced.

[0052] The obtained graphene fibers are brittle fibers with an elongation at break of less than 1%.

[0053] The above embodiments describe in detail the structure, features and effects of the present invention. The above are only preferred embodiments of the present invention. Any changes made in accordance with the concept of the present invention, or modifications to equivalent embodiments with equivalent changes, which do not exceed the scope covered by the specification, should be within the scope of protection of the present invention.

Claims

1. A method for preparing a self-twisted high thermal conductivity flexible graphene fiber, characterized in that: The following steps are involved: (1) adding water as a second phase to an organic phase graphene oxide dispersion and mixing them uniformly to obtain a graphene oxide two-phase spinning solution; the water accounts for 1% to 15% of the total solvent volume; the solvent of the organic phase graphene oxide dispersion is one of N,N-dimethylformamide, N,N-dimethylacetamide, tetrahydrofuran, dimethyl sulfoxide, N-methylpyrrolidone, ethylene glycol, diethylene glycol, and pyridine; (2) Extruding the graphene oxide dual-phase spinning solution through an extended spinning head into a coagulation bath, pulling it out to dry after sufficient coagulation, and continuously collecting it onto a roller to obtain self-twisted graphene oxide fibers; the coagulation bath is immiscible with water; (3) sending the dried self-twisted graphene oxide fibers into a reduction bath for continuous in-situ chemical reduction, and collecting the self-twisted reduced graphene oxide fibers; (4) The reduced graphene oxide fibers are graphitized in a high-temperature inert gas atmosphere to obtain self-twisted graphene fibers.

2. The preparation method according to claim 1, characterized in that The concentration of the graphene oxide dual-phase spinning solution is 3 mg / g-20 mg / g.

3. The preparation method according to claim 1, characterized in that The length of the extended spinning head in step (2) is 1 cm to 5 cm.

4. The preparation method according to claim 1, characterized in that The coagulation bath in step (2) comprises one or more of ethyl acetate, dichloromethane, n-hexane, cyclohexane, toluene, n-butanol, carbon tetrachloride, benzene, chloroform, cyclopentane, dichloroethane, ether, n-heptane, isooctane, pentane, tetrachloroethane, trichloroethane, and xylene.

5. The preparation method according to claim 1, characterized in that The reducing bath in step (3) includes one or more of vitamin C, hydroiodic acid, and hydrazine hydrate.

6. The preparation method according to claim 1, characterized in that The graphitization process of step (4) is to perform carbonization treatment at 1000°C-1200°C under the protection of inert gas, and then perform graphitization treatment at 3000°C.

7. A self-twisted high thermal conductivity flexible graphene fiber prepared by the preparation method as claimed in claim 1.

Images