Self-twisting high-thermal-conductivity flexible graphene fiber and preparation method thereof

Abstract

The invention discloses a self-twisting high-thermal-conductivity flexible graphene fiber and a preparation method thereof. Water is added into an organic-phase graphite oxide spinning solution, an organic phase and a water phase exist in the gel fiber in the solidification and drying process at the same time, the solvent concentration gradient and the surface tension gradient exist on the fiber surface due to the non-uniformity of the volatilization rate of a dual-phase solvent, and the non-uniformity causes the Mallangori effect and enables the gel fiber to generate rotary self-twisting. According to the method, controllable adjustment of the fiber twist can be realized by adjusting the water content of the initial spinning solution, and the self-twisted fiber is subjected to chemical reduction and graphitization treatment, so that the high-thermal-conductivity flexible graphene fiber can be obtained.

Description

Technical Field

[0001] The 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 has an extremely high electrical conductivity, far exceeding traditional conductors such as copper, making it an ideal material for the next generation of electronic devices and high-efficiency batteries. Graphene also has excellent thermal conductivity and can effectively dissipate heat, so it performs well in heat dissipation materials and thermal management. In addition, graphene has extremely high mechanical strength, with a tensile strength hundreds of times that of steel, but is very light, which makes it important for lightweight materials and structural reinforcement.

[0003] As a new type of fiber made of graphene material, graphene fiber combines the excellent properties of graphene and the flexibility of fiber. Due to its unique two-dimensional structure, graphene fiber has extremely high electrical conductivity, thermal conductivity and mechanical strength, and can withstand huge tensile and bending loads while remaining lightweight. These characteristics make graphene fiber show a wide range of application potential in many fields. In particular, it shows broad application prospects in the fields of flexible electronics and sensors. However, the current elongation at break of graphene fiber is less than 1%, which belongs to brittle materials. Its excellent electrical and thermal conductivity and other properties are difficult to be applied in flexible fields. Although some existing twisting technologies can improve the elongation at break of graphene fiber to a certain extent, the defect introduced by the subsequent twisting is that the strength of the fiber is greatly reduced, and it cannot meet the basic requirements of weaving for fiber strength, which seriously hinders the application and development of graphene fiber in the fields of flexible high thermal conductivity and electronics. Summary of the invention

[0004] In view of the defects of the prior art that a post-twisting device is required to prepare twisted graphene fibers, which is complicated and the strength of the prepared twisted graphene fibers is significantly reduced, the present invention provides a self-twisted 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 of the fibers, the non-uniform 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. Then, through subsequent chemical reduction and graphitization processes, high-strength, high-breaking elongation, high thermal conductivity, 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 conductive flexible graphene fiber, which is characterized by comprising the following steps: (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; (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 highly oriented along the axial direction due to the shearing action of the tube wall in the extended spinning head. After sufficient coagulation, the graphene oxide gel fiber with neatly arranged sheets containing the two-phase solvent is obtained; then it is pulled out for drying and continuously collected on the 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 self-twisting graphene oxide fibers;

[0007] (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.

[0008] 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.

[0009] Furthermore, the concentration of the graphene oxide dual-phase spinning solution is 3 mg / g-20 mg / g.

[0010] Furthermore, the length of the extended spinning head in step 2 is 1cm-5cm.

[0011] 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, dipropanol, tetrachloroethane, trichloroethane, and xylene.

[0012] Furthermore, the reducing bath in step 3 comprises one or more of acetic acid, trifluoroacetic acid, vitamin C, hydroiodic acid, and hydrazine hydrate.

[0013] Furthermore, the graphitization process of step 5 is to first perform a carbonization treatment at 1000°C-1200°C and then perform a graphitization treatment at 3000°C under the protection of an inert gas.

[0014] 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.

[0015] The fiber wrinkles prepared are oriented along the radial direction of the fiber, and gradually transition to the axial direction of the fiber during the stretching process, thereby giving the fiber a high elongation at break. In the extended spinning head, the shear force of the tube wall causes the sheets to be neatly arranged along the fiber axis. In the later spiral induction process, the fiber sheets are still neatly arranged along the spiral direction. The regular stacking of the sheets allows the fiber to maintain a high level of strength while having a high elongation at break.

[0016] Beneficial effects of the present invention: (1) By introducing the aqueous phase into the organic phase spinning solution system and cleverly utilizing the difference in surface tension and evaporation rate between the two phases of solvent, the Marangoni effect is induced, which drives the self-twisting of the macro gel fiber. This is a new method and system for preparing self-twisting fibers.

[0017] (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 fiber production efficiency and flexibility.

[0018] (3) Compared with the method of subsequent additional twisting, the large gaps and defects introduced by twisting the fibers after they are fully dried are avoided.

[0019] (4) By using an extended spinning head, the sheet layer 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 a high breaking strength while maintaining a high breaking elongation. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 Flow chart of preparation of Marangoni self-twisted fibers; Figure 2 Digital camera photos of the self-twisting areas of gel fibers with different water contents; Figure 3 SEM photo of microscopic spiral wrinkles of high thermal conductivity flexible fiber; Figure 4 Elongation at break of fibers with different water contents (after heat treatment at 3000°C); Figure 5 Thermal conductivity of fibers with different water contents (after heat treatment at 3000°C); Figure 6 Electrical conductivity of fibers with different water contents (after heat treatment at 3000℃). DETAILED DESCRIPTION

[0021] The following examples are used to further illustrate the present invention, and 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 parts by weight and weight percentages are used below.

[0022] The raw materials used in the present invention, unless otherwise specified, are conventional commercially available products; the methods used in the present invention, unless otherwise specified, are conventional methods in the art.

[0023] The embodiments of the present invention are further described below with reference to a plurality of embodiments.

[0024] It should be clear that the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in the field without creative work are within the scope of protection of the present application.

[0025] 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", "said" 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 other meanings.

[0026] Example 1 (1) preparing a graphene oxide dispersion with a concentration of 3 mg / g and a solvent of N,N-dimethylformamide; 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%; (2) The above-mentioned two-phase spinning solution is loaded into a degassing device and a syringe, and a needle with a length of 1 cm and a diameter of 130 μm is used as a spinning head to squeeze the spinning solution into an ethyl acetate coagulation bath. After sufficient coagulation, a gel fiber containing two-phase components of ethyl acetate and second phase solvent water is obtained; (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, the camera photo shows that the drying fiber shows light and dark changes under the light due to the spiral structure; (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.

[0027] (5) The reduced graphene oxide was placed in an inert gas argon atmosphere and first carbonized at 1200°C and then graphitized at 3000°C to obtain high thermal conductivity flexible graphene fibers. The elongation at break was 25%, the strength was 1.23 GPa, the conductivity was 0.89×106 S / m, and the thermal conductivity was 966 W / m K.

[0028] Example 2 (1) preparing a graphene oxide dispersion with a concentration of 8 mg / g and a solvent of dimethyl sulfoxide; adding 5% by mass of deionized water to the dispersion and mixing them evenly to obtain a GO two-phase spinning solution with a second phase water content of 5%; (2) The above two-phase spinning solution is loaded into a degassing device and a syringe, and a needle with a length of 5 cm and a diameter of 130 μm is used as a spinning head to squeeze the spinning solution into a n-hexane coagulation bath. After sufficient coagulation, a gel fiber containing two-phase components of n-hexane and a second phase solvent of water is obtained; (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, the camera photo shows that the drying fiber shows light and dark changes under the light due to the spiral structure; (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.

[0029] (5) The reduced graphene oxide was placed in an inert gas argon atmosphere and first carbonized at 1000°C and then graphitized at 3000°C to obtain a highly thermally conductive flexible graphene fiber. The elongation at break was 24%. The strength was 1.32 GPa, the conductivity was 0.9×106 S / m, and the thermal conductivity was 987 W / m K.

[0030] Example 3 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%.

[0031] The obtained graphene fiber 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.

[0032] Example 4 This comparative example is the same as Example 1, except that the proportion of the second phase water is 15%.

[0033] The obtained graphene fiber has a breaking elongation of 32%, a strength of 1.02 GPa, a conductivity of 0.86×106 S / m, and a thermal conductivity of 921 W / m K. Comparative Example 1 This comparative example is the same as Example 1, except that the second phase solvent water is not introduced.

[0034] The obtained graphene fibers are brittle fibers with a breaking elongation of less than 1%.

[0035] 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 protection scope 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; (2) The graphene oxide dual-phase spinning solution is squeezed into a coagulation bath through a spinning head through an extended spinning head, and after being fully coagulated, it is pulled out and dried, and continuously collected on a roller to obtain a self-twisted graphene oxide fiber; (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 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.

3. 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.

4. The preparation method according to claim 1, characterized in that: The length of the extended spinning head in step 2 is 1cm-5cm.

5. The preparation method according to claim 1, characterized in that: The coagulation bath in step 2 is immiscible with water and includes 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, dipropanol, tetrachloroethane, trichloroethane, and xylene.

6. The preparation method according to claim 1, characterized in that: The reducing bath in step 3 comprises one or more of acetic acid, trifluoroacetic acid, vitamin C, hydroiodic acid, and hydrazine hydrate.

7. The preparation method according to claim 1, characterized in that: The graphitization process of step 5 is to perform a carbonization treatment at 1000°C-1200°C under the protection of an inert gas, and then perform a graphitization treatment at 3000°C.

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

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