US20240060215A1

US20240060215A1 - Composite fiber and method of manufacturing same

Info

Publication number: US20240060215A1
Application number: US18/119,121
Authority: US
Inventors: Hong Chan JEON; Sang Soo Jeon; Hyun Dae Cho; Jee Jung Kim; So La CHUNG; Jin Ho Hwang; Tae Hee Han; Woo Jae Jeong; Dong Jun Kang; Hwan Soo Shin
Original assignee: Hyundai Motor Co; Industry University Cooperation Foundation IUCF HYU; Kia Corp
Current assignee: Hyundai Motor Co; Industry University Cooperation Foundation IUCF HYU; Kia Corp
Priority date: 2022-08-16
Filing date: 2023-03-08
Publication date: 2024-02-22
Also published as: KR20240023815A; DE102023106241A1; CN117587540A

Abstract

Disclosed is a composite fiber including a substrate and a MXene disposed inside the substrate. The substrate contains a polymer and has a fiber shape. Since the MXene content is controlled to be in an optimum range, the mechanical properties, mechanical stability, and oxidation stability of the composite fiber are maximized.

Description

CROSS REFERENCE TO RELATED APPLICATION

The present application claims priority to Korean Patent Application No. 10-2022-0101971, filed Aug. 16, 2022, the entire contents of which is incorporated herein for all purposes by this reference.

TECHNICAL FIELD

The present disclosure relates to a composite fiber and a method of manufacturing the same.

BACKGROUND

A MXene is a novel two-dimensional material with high electroconductivity and electrochemical properties similar to those of metals. A MXene exhibits excellent performance in many applications such as electrochemical energy storage devices, electrodes, gas and moisture sensors, and conductive fillers.
In addition, a MXene has excellent dispersibility due to hydrophilic functional groups present on the surface thereof. For example, a highly dispersed MXene solution can be used for fiber preparation. However, although each MXene layer has superior performance, the fiber produced therefrom exhibits weak mechanical properties and very poor oxidation stability. Therefore, to use MXenes for electric wires, electric heating and exthothermic materials, and wearable electronic materials, the chemical stabilization and mechanical properties of the MXene must be improved.

SUMMARY

In preferred aspects, provided is a composite fiber having improved mechanical properties by mixing MXene and a polymer and filling voids (e.g., spaces between layers) in the MXene with the polymer.
The term “MXene” as used herein refers to an inorganic material including multiple layers each of which is made of inorganic compounds such as halides, carbides, nitrides, or carbonitrides of transition metals (e.g., Ti, Cr, Mo, V, Nb, W, Y, Ta, Sc, etc.). The layers in MXene are in form of sheets, i.e. in two dimensional, which may be separated with void space between each layer and/or stacked with two or more layers. In certain embodiments, each layer of the MXene may have a thickness in nanometer range (e.g., 1 to 500 nm, 1 to 100 nm, or 1 to 10 nm) or in micrometer range (e.g., 1 to 500 μm, 1 to 100 μm, or 1 to 10 μm). A term “sheet-type” as used herein refers to a three-dimensional shape of a sheet, film or a thing layer, which has a planar surface and a substantially reduced thickness (e.g., millimeter, micrometer, or nanometer scale) compared to a width or a length of the planar surface.
However, the objectives of the present disclosure are not limited the ones described above. The objectives of the present disclosure will become more apparent from the following description and will be realized by the means described in the claims and combinations thereof.
In an aspect, provided is a composite fiber including: a substrate including a polymer and having a fiber shape; and MXene disposed in the substrate. The composite fiber may include the MXene in an amount of about 10% to 40% by weight based on the total weight of the composite fiber.
The polymer may include polyacrylonitrile (PAN).
The MXene may include a stack of two or more of nanosheets, and the polymer may be disposed between the nanosheets.
The polymer and the MXene may be bonded by electrostatic interaction.
A cross section of the composite fiber may have a solid circular shape, a hollow circular shape, a solid oval shape, a hollow oval shape, a hollow shape, or a line shape.
The composite fiber may have an electrical conductivity in a range of about 10 S/cm to 200 S/cm.
The composite fiber may have a tensile strength in a range of about 20 MPa to 400 MPa.
The composite fiber may have a density in a range of about 1.0 g/cm to 2.5 g/cm.
In an aspect, provided is a method of manufacturing the composite fiber as described herein. The method may include preparing a first dispersion solution including a polymer and a first solvent; preparing a second dispersion solution including a polymer and a second solvent; obtaining an admixture including the first dispersion solution and the second dispersion solution; and obtaining the composite fiber by wet spinning the admixture. The composite fiber includes a substrate including a polymer and having a fiber shape, and MXene dispersed in the substrate. Preferably, the composite fiber may suitably include the MXene in an amount of about 10% to 40% by weight based on the total weight of the composite fiber.
The first solvent may include one or more solvents selected from the group consisting of 1-methyl-2-pyrrolidinone-m-Methyl-2-pyrrolidone (NMP), N,N-dimethylformamide (DMF), dimethylacetamide (DMAc), and dimethyl sulfoxide (DMSO).
A concentration of the Mxene in the first dispersion solution may range from about 10 mg/mL to about 45 mg/mL.
The second solvent may include one or more solvents selected from the group consisting of 2-methyl-2-pyrrolidinone-m-Methyl-2-pyrrolidone (NMP), N,N-dimethylformamide (DMF), dimethylacetamide (DMAc), and dimethyl sulfoxide (DMSO).
A concentration of the polymer in the second dispersion solution may range from about 50 mg/mL to about 500 mg/mL.
The admixture may include the MXene in an amount of about 10% to 60% by weight based on the total weight of the admixture.
The composite fiber may be obtained by wet spinning the admixture into a coagulation fluid.
The coagulation fluid may include one or more selected from the group consisting of water, acetone, methyl alcohol, ethyl alcohol, isopropyl alcohol, methyl acetate, ethyl acetate, propyl acetate, acetic acid, acetonitrile, 1-Methyl-2-pyrrolidinone-N-Methyl-2-pyrrolidone (NMP), N,N-Dimethylformamide (DMF), dimethylacetamide (DMAc), dimethyl sulfoxide (DMSO), and tetrahydrofuran (THF).
The coagulation fluid may have a temperature in a range of about 20° C. to 60° C.
The wet spinning may be performed using a spinneret having a diameter in a range of about 10 to 1500 μm.
The method may further include heat treating the composite fiber in an inert gas atmosphere at a temperature in a range of 400° C. to 600° C.
The composite fiber according to various exemplary embodiments of the present disclosure has significantly improved mechanical properties and oxidation stability. The additional heat treatment improves electrical conductivity and mechanical properties of the composite fiber.
However, the advantages of the present disclosure are not limited thereto. It should be understood that the advantages of the present disclosure include all effects that can be inferred from the description given below.
Other aspects of the invention are disclosed infra.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an exemplary method for manufacturing an exemplary composite fiber according to an exemplary embodiment of the present disclosure;

FIG. 2 is a photograph of a cross section of a composite fiber according to Preparation Example 1 of the present disclosure;

FIG. 3 is a photograph of a cross section of a composite fiber according to Preparation Example 5 of the present disclosure;

FIG. 4 is a photograph of a cross section of a composite fiber according to Preparation Example 6 of the present disclosure;

FIG. 5 is a view illustrating tensile strength values of composite fibers according to Preparation Example 1, 7, 8 of the present disclosure;

FIG. 6 is a photograph of a cross section of a composite fiber according to Preparation Example 7 of the present disclosure;

FIG. 7 is a photograph of a cross section of a composite fiber according to Preparation Example 8 of the present disclosure;

FIG. 9 is a photograph of a cross section of a composite fiber according to Preparation Example 1 of the present disclosure;

FIG. 10 is a photograph of a cross section of a composite fiber according to Preparation Example 2 of the present disclosure;

FIG. 11 is a photograph of a cross section of a composite fiber according to Preparation Example 3 of the present disclosure;

FIG. 12 is a photograph of a cross section of a composite fiber according to Preparation Example 4 of the present disclosure;

FIG. 13 is a photograph of a cross section of a composite fiber according to Preparation Example 9 of the present disclosure;

FIG. 14 is a photograph of a cross section of a composite fiber according to Preparation Example 10 of the present disclosure;

FIG. 15 is a photograph of a cross section of a composite fiber according to Preparation Example 11 of the present disclosure;

FIG. 16 is a photograph of a cross section of a composite fiber according to Preparation Example 12 of the present disclosure;

FIG. 17 is a view illustrating tensile strength values of composite fibers according to Preparation Examples 1 to 4 and 9 to 12 of the present disclosure;

FIG. 18 is a view illustrating tensile strength values of composite fibers according to Preparation Examples 1 to 4 and 9 to 12 of the present disclosure;

FIG. 19 is a view illustrating electrical conductivity values of composite fibers according to Preparation Examples 1 to 4 and 9 to 12 of the present disclosure; and

FIG. 20 is a view illustrating density values of composite fibers according to Preparation Examples 1 to 4 and 9 to 12 of the present disclosure.

DETAILED DESCRIPTION

Above objectives, other objectives, features, and advantages of the present disclosure will be readily understood from the following preferred embodiments associated with the accompanying drawings. However, the present disclosure is not limited to the embodiments described herein and may be embodied in other forms. The embodiments described herein are provided so that the disclosure can be made thorough and complete and that the spirit of the present disclosure can be fully conveyed to those skilled in the art.
Throughout the drawings, like elements are denoted by like reference numerals. In the accompanying drawings, the dimensions of the structures are larger than actual sizes for clarity of the present disclosure. Terms used in the specification, “first”, “second”, etc., may be used to describe various components, but the components are not to be construed as being limited to the terms. These terms are used only for the purpose of distinguishing a component from another component. For example, without departing from the scope of the present disclosure, a first component may be referred as a second component, and a second component may be also referred to as a first component. As used herein, the singular forms “a”, “an”, and “the” are intended to include the plural forms as well unless the context clearly indicates otherwise.
It will be further understood that the terms “comprises”, “includes”, or “has” when used in this specification specify the presence of stated features, regions, integers, steps, operations, elements and/or components, but do not preclude the presence or addition of one or more other features, regions, integers, steps, operations, elements, components and/or combinations thereof. It will also be understood that when an element such as a layer, film, area, or sheet is referred to as being “on” another element, it can be directly on the other element, or intervening elements may be present therebetween. Similarly, when an element such as to a layer, film, area, or sheet is referred to as being “under” another element, it can be directly under the other element, or intervening elements may be present therebetween.
Unless otherwise specified, all numbers, values, and/or representations that express the amounts of components, reaction conditions, polymer compositions, and mixtures used herein are to be taken as approximations including various uncertainties affecting measurement that inherently occur in obtaining these values, among others, and thus should be understood to be modified by the term “about” in all cases.
Further, unless specifically stated or obvious from context, as used herein, the term “about” is understood as within a range of normal tolerance in the art, for example within 2 standard deviations of the mean. “About” can be understood as within 10%, 9%, 8%, 7%, 6%, 5%, 4%, 3%, 2%, 1%, 0.5%, 0.1%, 0.05%, or 0.01% of the stated value. Unless otherwise clear from the context, all numerical values provided herein are modified by the term “about.”
Furthermore, when a numerical range is disclosed in this specification, the range is continuous, and includes all values from the minimum value of said range to the maximum value thereof, unless otherwise indicated. Moreover, when such a range pertains to integer values, all integers including the minimum value to the maximum value are included, unless otherwise indicated. In the present specification, when a range is described for a variable, it will be understood that the variable includes all values including the end points described within the stated range. For example, the range of “5 to 10” will be understood to include any subranges, such as 6 to 10, 7 to 10, 6 to 9, 7 to 9, and the like, as well as individual values of 5, 6, 7, 8, 9 and 10, and will also be understood to include any value between valid integers within the stated range, such as 5.5, 6.5, 7.5, 5.5 to 8.5, 6.5 to 9, and the like. Also, for example, the range of “10% to 30%” will be understood to include subranges, such as 10% to 15%, 12% to 18%, 20% to 30%, etc., as well as all integers including values of 10%, 11%, 12%, 13% and the like up to 30%, and will also be understood to include any value between valid integers within the stated range, such as 10.5%, 15.5%, 25.5%, and the like. In an aspect, a composite fiber includes: a substrate containing a polymer and having a fiber shape; and MXene disposed in the substrate.
Maxine is a novel two-dimensional material with high electroconductivity and electrochemical properties similar to metals. Since the surface of the MXene is hydrophilic and has negatively charged to functional groups such as OH, 0, and F, the MXene can be easily dispersed and assemble into a three-dimensional structure. In addition, since the MXene does not require post-treatment unlike graphene oxide, the processing cost thereof is low. When a three-dimensional structure is made from fibers, the electrical and mechanical properties of the structure are not good. The poor physical properties are due to the fact that the MXene is a stack of multiple nanosheets each of which a gap is provided. Due to the gap between each of the nanosheets, the MXene has a small binding force.
Accordingly, to solve the problem of poor physical properties of MXenes, the present disclosure provides a method of mixing a MXene and a polymer so that interlayer gaps of the MXene can be filled with the polymer, thereby improving the physical properties of the MXene.
The composite fiber may suitably include MXene in an amount of about 10% to 40% by weight based on the total weight of the composite fiber. When the content of the MXene is less than about 10% by weight, the MXene may have poor electrical conductivity due to high resistance. When the content of the MXene is greater than about 40% by weight, the MXene acts as an impurity, which may cause the problem of fiber breakage during the formation of a fibrous structure.
The polymer may include one or more polymers selected from all polymers produced by polymerization of monomers having a GN functional group. For example, the polymer may be polyacrylonitrile (PAN).
The polymer and the MXene may be bonded by electrostatic interaction.
Due to the electrostatic interaction bonding between the functional group —OH or —O of the MXene and the functional group —C≡N— of the polymer, the dispersibility of the composite fibers may be improved.
A cross section of the composite fiber may have a solid circular shape, a solid oval shape, a hollow shape, or a line shape.
Specifically, in the present disclosure, when the composite fiber has a circular cross section or a line-shaped cross section, the aspect ratio is in a range of about 1 to 30.
The composite fiber may have an electrical conductivity in a range of about 10 S/cm to 200 S/cm.
The composite fiber may have a tensile strength in a range of about 20 MPa to 400 MPa.
The composite fiber may have a density in a range of about 1.0 g/cm to 2.5 g/cm.
In an aspect, provided is a method of manufacturing the composite fiber as described herein. In describing the method, since a substrate including a polymer and a MXene are the same as those described above, a detailed description thereabout will not be redundantly given below.
FIG. 1 shows an exemplary manufacturing method for an exemplary composite fiber according to an exemplary embodiment of the present disclosure. As shown in FIG. 1 , an exemplary manufacturing method includes: preparing a first dispersion solution including a polymer and a first solvent; preparing a second dispersion solution including a polymer and a second solvent; obtaining an admixture including the first dispersion solution and the second dispersion solution; and obtaining a composite fiber by wet spinning the admixture. The composite fiber includes a substrate including a polymer and having a fiber shape and a MXene dispersed in the substrate and includes the MXene in an amount of 10% to 40% by weight based on the total weight of the composite fiber.
First, S10 is a step of preparing a first dispersion solution including a MXene and a first solvent.
The first dispersion solution may include the MXene in a concentration of about 10 mg/mL to 45 mg/mL. When the concentration of the MXene is less than about 10 mg/mL, when being mixed with the polymer, a low-viscosity admixture is prepared, and thus spinning performance is not good. When the concentration of the MXene is greater than about 45 mg/mL, the MXene and the polymer may agglomerate, and the viscosity is excessively high. Therefore, spinning performance is not good.
The first solvent may include one or more solvents selected from the group consisting of 1-methyl-2-pyrrolidinone-m-Methyl-2-pyrrolidone (NMP), N,N-dimethylformamide (DMF), dimethylacetamide (DMAc), and dimethyl sulfoxide (DMSO).
MXenes have excellent dispersibility in water because the surfaces of the MXenes are terminated by hydrophilic functional groups. However, a high-concentration water-MXene dispersion is practically difficult to use. The reason for this is that redispersion in water is difficult. In addition, it is difficult to prepare a homogeneous dispersion because the nanosheets in the MXene easily agglomerate with each other. Therefore, in the present disclosure, an organic solvent may be used as the first solvent.
Next, S20 is a step of preparing a second dispersion solution including a polymer and a second solvent.
The second dispersion solution may include the polymer in a concentration of about 50 mg/mL to 500 mg/mL. When the concentration of the polymer is less than about 50 mg/mL, the admixture may not coagulate. When the concentration of the polymer is greater than about 500 mg/mL, the admixture may not be uniformly spun due to high conductivity.
The second solvent may include one or more solvents selected from the group consisting of 2-methyl-2-pyrrolidinone-m-Methyl-2-pyrrolidone (NMP), N,N-dimethylformamide (DMF), dimethylacetamide (DMAc), and dimethyl sulfoxide (DMSO).
As described above, the polymer may include polyacrylonitrile (PAN). As the second solvent, an organic solvent may be used because the polyacrylonitrile (PAN) is not dispersed in moisture.
Next, Step S30 is a step of obtaining an admixture including the first dispersion solution and the second dispersion solution.
When each of the first dispersion solution and the second dispersion solution uses an organic solvent, the dispersions are stable at high concentrations. For example, a homogeneous admixture that is free of MXene agglomeration can be obtained. In addition, since a MXene dispersed in an organic solvent has a high affinity to a polyacrylonitrile solution due to the functional groups present on the surface thereof, a stable admixture can be obtained. That is, an admixture having excellent solution stability can be obtained, a high concentration spinning solution can be obtained, and an admixture with a high oxidation stability can be obtained.
The admixture may include the MXene in an amount of about 10% to 60% by weight based on the total weight of the admixture. For example, the MXene content may be in a range of about 10% to 50% by weight or particularly a range of about 20% to 60% by weight based on the total weight of the admixture. When the MXene content is less than about 10% by weight, the conductivity may be reduced due to an increase in electrical resistance. When the MXene content is greater than about 60% by weight, it is difficult to obtain a fiber spinning gel, and thus spinning cannot be performed.
Finally, Step S40 is a step of wet spinning the admixture to obtain composite fibers.
In step S40, composite fibers are obtained by wet spinning the admixture in a coagulation fluid.
The term “wet spinning” as used herein means a technique in which a pressure is applied to the admixture so that the admixture can be spun into the coagulation fluid that is capable of coagulating the admixture, through a spinneret (spinning nozzle). In the coagulation fluid, as the solvent in the admixture diffuses, solidification and precipitation occur to form fibers.
The admixture may be spun at a speed in a range of about 0.1 mL/h to 35 mL/h. When the spinning speed is greater than about 35 mL/h, there is a problem that the mixing solution is not subjected to a constant shear stress, resulting in uneven fibers.
The coagulation fluid may include one or more selected from the group consisting of water, acetone, methyl alcohol, ethyl alcohol, isopropyl alcohol, methyl acetate, ethyl acetate, propyl acetate, acetic acid, acetonitrile, 1-Methyl-2-pyrrolidinone-N-Methyl-2-pyrrolidone (NMP), N,N-Dimethylformamide (DMF), dimethylacetamide (DMAc), dimethyl sulfoxide (DMSO), and tetrahydrofuran (THF). For example, the coagulation fluid may contain water and ethanol mixed in a volume ratio in a range of about 3:7 to 7:3.
The coagulation fluid may have a temperature in a range of from about 20° C. to about 60° C. When the temperature of the coagulation fluid is below 20° C., the coagulation rate is low. Therefore, irregular shrinkage occurs during a drying process to remove the residual solvent. When the temperature of the coagulation fluid is above about 60° C., the solvent rapidly escapes from the surface of the fiber because the solvent rapidly diffuses in the coagulation fluid. In this case, the solvent may remain in the fiber due to fast solidification, which may result in deterioration in physical properties of the fiber.
The wet spinning may be performed using a spinneret having a diameter in a range of about 10 μm to 1500 μm. For example, the diameter may be in a range of about 100 μm to 1000 μm or particularly a range of about 100 μm to 500 μm. Preferably, the diameter may be in a range of about 100 μm to 410 μm. When the diameter of the spinneret is less than about 10 μm, a problem may occur that spinning through the nozzle does not proceed. When the diameter is greater than about 1500 μm, the degree of orientation and density of the fibers may be lowered due to insufficient shear stress, and thus mechanical properties of the fibers may be deteriorated.
The composite fibers may be elongated 1 to 20 times. The elongation can improve the degree of alignment of the nano sheets in the MXene and the polymer along the axial direction of the fiber, i.e., the degree of orientation.
The method may further include heat treating the composite fibers in an inert gas atmosphere.
Through this heat treatment, cyclization and carburization of the polyacrylonitrile may improve the mechanical properties. In particular, in the case of the MXene, the functional groups on the surface of the MXene are partially removed. Therefore, oxidation stability due to moisture may be improved, and the gaps between the nanosheets are narrowed. As a result, an electron hopping distance is reduced, and thus the electrical properties are improved. In addition, since the gap between the sheets is narrowed, that is, the sheets are densely arranged, the mechanical properties of the sheets are improved.
The heat treatment may be performed in a temperature range of about 400° C. to 600° C. When the heat treatment temperature is less than 400 about ° C., the cyclization reaction of the PAN does not occur, resulting in a deterioration in the electrical conductivity and mechanical properties. When the heat treatment temperature is greater than about 600° C., the normal cyclization products of the PAN cannot be obtained.
The inert gas may include argon (Ar), nitrogen (N), and the like.
The heat treatment may be performed for a period of about 30 minutes to 2 hours while the temperate is raised at a rate of about 1° C./min to 10° C./min.
Although the composite fibers are not limited in their applications, the composite fibers may be used for wearable fiber materials, electric wires, and heating wires. In addition, the composite fibers can find applications in automotive industry, aerospace industry, various cables, and electrical products.

EXAMPLE

Hereinafter, the present disclosure will be described in more detail with reference to the following preparation examples. However, the technical idea of the present disclosure is not limited thereto.

Preparation Examples 1 to 4

Admixtures of Preparation Examples 1 to 4 were prepared by mixing a first dispersion solution containing a MXene and dimethylsulfoxide and having a concentration of 9.09 mg/mL and a second dispersion solution containing polyacrylonitrile and dimethylsulfoxide and having a concentration of 100 mg/mL. The admixtures have different MXene contents.

TABLE 1

Admixture Preparation Example	Maxine Content in Admixture

Admixture Preparation Example 1	10% by weight
Admixture Preparation Example 2	20% by weight
Admixture Preparation Example 3	30% by weight
Admixture Preparation Example 4	40% by weight

Composite Fiber Preparation Examples 1 to 4
Each of the admixtures of Examples 1 to 4 was poured in a plastic syringe equipped with a spinneret having a diameter of 100 μm. The admixture in the syringe was spun into a coagulation bath at a rate of 15 mL/h using an injection pump to obtain a composite fiber. In this case, the temperature of a coagulation fluid in the coagulation bath was 20° C., and the coagulation fluid was a mixture of water and ethanol mixed in a volume ratio of 3:7. The composite fibers of Preparation Examples 1 to 4 were dried using a drying heater at 60° C. and then dried again at 80° C. for thermal fixation.

TABLE 2

Composite Fiber	Admixture	Maxine content
Preparation Example	Preparation Example	in admixture

Composite Fiber Preparation	Admixture Preparation		10% by weight
Examples 1	Example 1
Composite Fiber Preparation	Admixture Preparation		20% by weight
Examples 2	Example 2
Composite Fiber Preparation	Admixture Preparation		30% by weight
Examples 3	Example 3
Composite Fiber Preparation	Admixture Preparation		40% by weight
Examples 4	Example 4

Composite Fiber Preparation Examples 5 to 6
Composite fibers were prepared in the same manner as in Preparation Example 1 except that the diameter of the spinneret was changed.

TABLE 3

Composite Fiber	Admixture	Spinneret
Preparation Example	Preparation Example	diameter

Composite Fiber Preparation	Admixture Preparation		100 μm
Example 1	Example 1
Composite Fiber Preparation	Admixture Preparation		250 μm
Example 5	Example 1
Composite Fiber Preparation	Admixture Preparation	410 μm
Example 6	Example 1

Composite Fiber Preparation Examples 7 to 8
Composite fibers were prepared in the same manner as in Preparation Example 1 except that the temperature of the coagulation fluid was changed.

TABLE 4

Composite Fiber	Admixture	Coagulation
Preparation Example	Preparation Example	fluid Temperature

Composite Fiber Preparation	Admixture Preparation		20° C.
Example 1	Example 1
Composite Fiber Preparation	Admixture Preparation		40° C.
Example 7	Example 1
Composite Fiber Preparation	Admixture Preparation	60° C.
Example 8	Example 1

Composite Fiber Preparation Examples 9 to 12
Each of the admixtures of Examples 1 to 4 was poured in a plastic syringe equipped with a spinneret having a diameter of 100 μm. The admixture in the syringe was spun into a coagulation bath at a rate of 15 mL/h using an injection pump to obtain a composite fiber. In this case, the temperature of a coagulation fluid in the coagulation bath was 20° C., and the coagulation fluid was a mixture of water and ethanol mixed in a volume ratio of 3:7. The composite fibers of Preparation Examples 5 to 8 thus obtained were subjected to heat treatment at a temperature of 500° C. for 1 hour after the temperature was elevated at a rate of 5° C./min, with the composite fibers fixed at both ends not to contract and exposed to an argon atmosphere.

TABLE 5

Composite Fiber	Admixture	MXene content
Preparation Example	Preparation Example	in admixture

Composite Fiber Preparation	Admixture Preparation		10% by weight
Example 9	Example 1
Composite Fiber Preparation	Admixture Preparation		20% by weight
Example 10	Example 2
Composite Fiber Preparation	Admixture Preparation		30% by weight
Example 11	Example 3
Composite Fiber Preparation	Admixture Preparation		40% by weight
Example 12	Example 4

Experimental Example 1: Changes in Cross Section Morphology and Physical Properties of Composite Fibers According to Diameter of Spinneret

Changes in physical properties and cross section morphology of the composite fibers of Preparation Examples 1, 5, and 6 were observed. The obtained results are presented in Table 6 and FIGS. 2 to 4 .

TABLE 6

Composite Fiber	Spinneret	Tensile
Preparation Example	diameter	strength

Composite Fiber Preparation	100 μm	105 MPa
Example 1
Composite Fiber Preparation	250 μm	95 MPa
Example 5
Composite Fiber Preparation	410 μm	92 MPa
Example 6

FIGS. 2 to 4 are photographs of cross sections of composite fibers according to Preparation Examples 1, 5, and 6 of the present disclosure. Referring to Table 6 and FIGS. 2 to 4 , the shear stress increases according to the spinneret diameter regardless of the morphological change. It is found that the orientation and density of the fibers can be controlled by increasing the shear stress.

Experimental Example 2: Changes in Cross Section Morphology and Physical Properties of Composite Fibers According to Temperature of Coagulation Fluid

Changes in physical properties and cross section morphology of the composite fibers of Preparation Examples 1, 7, and 8 were observed. The results are shown in FIGS. 5 to 7 .
FIG. 5 is a view illustrating tensile strength values of the composite fibers of Preparation Examples 1, 7, and 8 of the present disclosure. FIGS. 6 to 7 are photographs of cross sections of the composite fibers of Preparation Examples 7 and 8 of the present disclosure. Referring to FIGS. 5 to 7 , as the temperature of the coagulation bath increases, the solvent exchange in gel fiber is accelerated, resulting in a nonuniform structure in the fiber. This results in deterioration in mechanical properties.

Experimental Example 3: Changes in Cross Section Morphology and Physical Properties of Composite Fibers According to Presence and Absence of Heat Treatment

Changes in physical properties and cross section morphology of the composite fibers of Preparation Examples 1 to 4 and 9 to 12 were observed. The results are shown in FIGS. 9 to 20 .
FIGS. 9 to 16 are photographs of cross sections of the composite fibers of Preparation Examples 1 to 4 and 9 to 12 of the present disclosure. FIGS. 17 to 20 are views illustrating physical properties of the composite fibers of Preparation Examples 1 to 4 and 9 to 12 of the present disclosure; Referring to FIGS. 9 to 16 , it is found that the heat treatment induces cyclization and dehydrogenation of PAN and thus improves mechanical, physical, and electrical properties of the composite fibers.
Referring to FIGS. 17 to 20 , the composite fibers of Preparation Examples 9 to 12 in which the heat treatment was performed exhibited better tensile strength, toughness, electrical conductivity, and density than the composite fibers of Preparation Examples 1 to 4 in which the heat treatment was not performed.
That is, since the mechanical properties of the polymer are improved due to the heat treatment, and the functional groups on the surface of the MXene are partially removed, the gap between the nanosheets of the MXene is narrowed. That is, the sheets in the MXene are more densely arranged. Therefore, the mechanical properties of the composite fibers are improved.
The composite fiber according to the present disclosure contain a substrate containing a polymer and having a fiber shape and a MXene disposed in the substrate in an optimum mixing ratio, thereby having improved physical properties and exhibiting improved mechanical and oxidation stability.
While exemplary embodiments of the present disclosure have been described with reference to the accompanying drawings, those skilled in the art will appreciate that the present disclosure can be implemented to in other different forms without departing from the technical spirit or essential characteristics of the exemplary embodiments. Therefore, it can be understood that the preparation examples described above are only for illustrative purposes and are not restrictive in all aspects.

Claims

What is claimed is:

1. A composite fiber comprising:

a substrate comprising a polymer and having a fiber shape; and

a MXene disposed inside the substrate,

wherein the composite fiber comprises the Mxene in an amount of about 10% to 40% by weight based on the total weight of the composite fiber.

2. The composite fiber of claim 1, wherein the polymer comprises polyacrylonitrile (PAN).

3. The composite fiber of claim 1, wherein the MXene comprises a stack comprising two or more nanosheets, wherein the polymer is disposed between the nanosheets.

4. The composite fiber of claim 1, wherein the polymer and the MXene are bonded by electrostatic interaction.

5. The composite fiber of claim 1, wherein a cross section of the composite fiber has a circular shape, a hollow circular shape, a solid oval shape, a hollow oval shape, a hollow shape, or a line shape.

6. The composite fiber of claim 1, wherein the composite fiber has an electrical conductivity in a range of about 10 S/cm and 200 S/cm, a tensile strength in a range of about 10 MPa to 200 MPa, and a density of about 1.0 g/cm to 2.5 g/cm.

7. A method of manufacturing a composite fiber, the method comprising:

preparing a first dispersion solution comprising a MXene and a first solvent;

preparing a second dispersion solution comprising a polymer and a second solvent;

obtaining an admixture comprising the first dispersion solution and the second dispersion solution; and

obtaining a composite fiber by wet spinning the admixture,

wherein the composite fiber comprises a substrate comprising a polymer having a fiber shape; and a MXene disposed in the substrate, wherein the composite fiber comprises the MXene in an amount of about 10% to 40% by weight based on the total weight of the composite fiber.

8. The method of claim 7, wherein the first solvent comprises one or more selected from the group consisting of 1-methyl-2-pyrrolidinone-m-Methyl-2-pyrrolidone (NMP), N,N-dimethylformamide (DMF), dimethylacetamide (DMAc), and dimethyl sulfoxide (DMSO).

9. The method of claim 7, wherein a concentration of the MXene in the first dispersion solution ranges from about 10 mg/mL to about 45 mg/mL.

10. The method of claim 7, wherein the second solvent comprises one or more selected from the group consisting of 2-methyl-2-pyrrolidinone-m-Methyl-2-pyrrolidone (NMP), N,N-dimethylformamide (DMF), dimethylacetamide (DMAc), and dimethyl sulfoxide (DMSO).

11. The method of claim 7, wherein a concentration of the polymer in the second dispersion solution ranges from about 50 mg/mL to about 500 mg/mL.

12. The method of claim 7, wherein the admixture comprises the MXene in an amount of 10% to 60% by weight based on the total weight of the admixture.

13. The method of claim 7, wherein the composite fiber is obtained in a manner to wet spin the admixture into a coagulation fluid, and

the coagulation fluid comprises one or more selected from the group consisting of water, acetone, methyl alcohol, ethyl alcohol, isopropyl alcohol, methyl acetate, ethyl acetate, propyl acetate, acetic acid, acetonitrile, 1-Methyl-2-pyrrolidinone-N-Methyl-2-pyrrolidone (NMP), N,N-Dimethylformamide (DMF), dimethylacetamide (DMAc), dimethyl sulfoxide (DMSO), and tetrahydrofuran (THF).

14. The method of claim 13, wherein the coagulation fluid has a temperature in a range of from about 20° C. to 60° C.

15. The method of claim 7, wherein the wet spinning is performed using a spinneret having a diameter in a range of about 10 μm to 1500 μm.

16. The method of claim 7, further comprising heat-treating the composite fiber in an inert gas atmosphere at a temperature in a range of about 400° C. to 600° C.

17. The method of claim 7, wherein the polymer comprises polyacrylonitrile (PAN).

18. The method of claim 7, wherein the MXene comprises a stack of two or more nanosheets, wherein the polymer is disposed between the nanosheets.

19. The method of claim 7, wherein the polymer and the MXene are bonded by electrostatic interaction.

20. The method of claim 7, wherein a cross section of the composite fiber comprises a circular shape, a hollow circular shape, a solid oval shape, a hollow oval shape, a hollow shape, or a line shape, and

wherein the composite fiber has an electrical conductivity in a range of about 10 S/cm and 200 S/cm, a tensile strength in a range of about 10 MPa to 200 MPa, and a density of about 1.0 g/cm to 2.5 g/cm.