Intelligent conductive fiber with skin-core structure and preparation method thereof

Abstract

The application relates to the field of preparation of conductive fibers, in particular to a smart conductive fiber with a skin-core structure and a preparation method thereof, which is prepared through coaxial spinning of carbon nanofiber / MXene dispersion liquid prepared from single-layer MXene nanosheet spinning slurry and carbon nanofiber and aramid nanofiber aramid nanometer monomer dispersion liquid prepared from aramid nanofiber and a solvent; in the carbon nanofiber / MXene dispersion liquid, MXene is dispersed in the carbon nanofiber; the skin layer of the smart conductive fiber is aramid nanofiber, and the core layer is a three-dimensional conductive network constructed by two-dimensional MXene nanosheets and one-dimensional carbon nanomaterials interspersed between the two-dimensional MXene nanosheets and connecting the two-dimensional MXene nanosheets; the core layer presents a microstructure of 'layer support'; the smart conductive fiber adopts high-strength and high-modulus aramid nanofiber as the skin layer and the frame structure, and MXene / carbon nanofiber as a functional material to endow the composite fiber with high conductivity; and the preparation method is simple.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of preparation of conductive fibers, in particular to a smart conductive fiber with a core-sheath structure and a preparation method thereof. BACKGROUND

[0002] With the vigorous development and huge demand of intelligent wearable electronic devices, various intelligent devices with sensitive sensing ability are emerging, which has driven a huge research boom. At the same time, the urgent need for simple and efficient preparation of intelligent electronic products has promoted the innovation in the field of sensing, not only updating the quantity of products, but also enriching the types of products. Compared with other common and mature sensors such as conductive films, hydrogels and aerogels, one-dimensional sensors are in the emerging stage. Benefiting from the superior characteristics such as stretchability, flexibility, lightweight and weavability, wearable sensor devices based on fibers and textiles have attracted much research attention. In addition, the conductive fiber has good adhesion with clothing and is soft and comfortable when in contact with human skin, which has significant advantages in human motion capture, sports, rehabilitation training, remote health monitoring and daily entertainment. Therefore, one-dimensional conductive materials, including fibers and yarns, show a vigorous development and bright prospect in the field of intelligent wearables.

[0003] MXene is a new type of two-dimensional high-conductive material composed of transition metal nitrides and carbides, with a general chemical formula of M n+ 1X n T x (n = 1-4). Wherein M is a transition metal element (such as Ti, Sc, Zr, Nb, etc.), X represents carbon, nitrogen or carbon-nitrogen element, T x represents the functional groups (-F, -O, -OH, -Cl, etc.) attached to its surface during the preparation process. Due to the rich hydrophilic functional groups on the surface, MXene nanosheets can be assembled into macroscopic MXene fibers, or can be compounded with other functional unit materials or matrix materials to prepare MXene composite fibers. MXene has good mechanical and electrical properties similar to graphene, and also has the characteristics of hydrophilic and solution processing like graphene oxide, and does not need a post-treatment reduction process, so MXene fibers are expected to become another kind of fiber material integrating structure and function after graphene fibers, meeting the needs of the field of intelligent wearables. However, the mechanical and electrical properties of MXene composite fibers are far inferior to the intrinsic properties of MXene nanomaterials, the main reason being that the wrinkles, disordered structures and weak interfacial forces between the layers generated during the assembly of MXene nanosheets often lead to the existence of pores and defects inside the MXene fibers and irregular fiber shape.

[0004] In the patent with publication number CN107938026A, a MXene fiber and its preparation method are specifically disclosed. The invention uses graphene oxide as a template, and small-size MXene layers are connected to each other under the assistance of graphene oxide, so that a MXene fiber with good conductivity and good mechanical properties can be continuously spun. However, the problem that MXene is easily oxidized is ignored. In the patent with publication number CN112144148A, a preparation method of a high-strength MXene fiber is specifically disclosed. The invention injects a MXene spinning slurry into a coagulation bath of a chitosan solution, and then immerses the obtained MXene fiber in a hydriodic acid solution, washes and dries it to obtain a high-strength MXene fiber. However, the conductivity of the prepared fiber is reduced to a certain extent, and the application scenarios and fields of the fiber have certain limitations.

[0005] CN109811426A discloses a conductive coaxial nanofiber with a core-sheath structure and a preparation method thereof. The invention provides a preparation method of a conductive fiber with a core-sheath structure, which comprises the following steps: 1) preparing a core layer spinning solution; 2) preparing a sheath layer spinning solution; 3) preparing a coaxial fiber; 4) high-temperature thermal reduction: obtaining a conductive coaxial nanofiber by high-temperature thermal reduction of the coaxial fiber obtained in step 3); i.e. the conductive fiber with a core-sheath structure disclosed in the invention. The method of the invention uses graphene oxide as a core layer material and a high-temperature resistant polymer as a sheath layer material, so that the graphene oxide in the core layer can be reduced by high-temperature thermal reduction, and the obtained fiber has flexibility, excellent conductivity and mechanical properties. However, since the spinning solution used is a graphene oxide aqueous solution, high-temperature thermal reduction is required to obtain the final fiber, so the method is relatively complex.

[0006] In summary, there is an urgent need to develop a method for preparing an intelligent conductive fiber with excellent mechanical and electrical properties, which is not easily oxidized and is simple to prepare. SUMMARY

[0007] In view of the above-mentioned deficiencies of the prior art, an intelligent conductive fiber with a skin-core structure and a preparation method thereof are provided. The intelligent conductive fiber has a skin-core structure, and the skin layer and the frame structure are made of high-strength and high-modulus aramid nanofiber. MXene / carbon nanofiber is used as a functional material to endow the composite fiber with high conductivity. The preparation method is simple.

[0008] To solve the above technical problems, the technical scheme adopted by the present application is that a smart conductive fiber with a skin-core structure is prepared by coaxial spinning of a carbon nanofiber / MXene dispersion liquid prepared from a single-layer MXene nanosheet spinning slurry and carbon nanofibers, and an aramid nanofiber monomer dispersion liquid prepared from aramid nanofibers and a solvent, wherein the MXene disperses the carbon nanofibers in the carbon nanofiber / MXene dispersion liquid; the skin layer of the smart conductive fiber is aramid nanofibers, and the core layer is a three-dimensional conductive network constructed by two-dimensional MXene nanosheets and one-dimensional carbon nanomaterials interspersed between the two-dimensional MXene nanosheets and connecting the two-dimensional MXene nanosheets, and the core layer presents a "layer support" microstructure.

[0009] The smart conductive fiber with a skin-core structure described above, wherein the aramid nanofibers are para-aramid fibers with a length of 5-10 mm.

[0010] The smart conductive fiber with a skin-core structure described above has a diameter of 1-2 mm.

[0011] The smart conductive fiber with a skin-core structure described above has an electrical conductivity of 1.42-2.12 x 10 5 S / m, a breaking strength of 197-285 MPa, and an elongation at break of 10%-12%.

[0012] The preparation method of the smart conductive fiber with a skin-core structure described above comprises the following steps:

[0013] (1) chemically etching a raw material MAX phase by an etchant, reacting under heating conditions, and preparing a single-layer MXene nanosheet spinning slurry through washing, oscillation peeling, and gradient centrifugal separation steps;

[0014] (2) diluting the single-layer MXene nanosheet spinning slurry with deionized water to 30-50 mg / mL -1 to form a carbon nanofiber / MXene dispersion liquid with single-layer MXene nanosheets and carbon nanofibers; the stirring reaction time is 1-2 h, and the ultrasonic time is 30-60 min; in the carbon nanofiber / MXene dispersion liquid, the mass fraction of the single-layer MXene nanosheets is 80-99%, and the mass fraction of the carbon nanofibers is 1-20%;

[0015] (3) adding para-aramid fibers to a solvent and reacting under magnetic stirring conditions to form a uniform aramid nanofiber dispersion liquid;

[0016] (4), the solution obtained in steps (2) and (3) is defoamed and then added into a syringe, the syringe is connected to a coaxial needle, and the fiber is formed by simultaneously injecting into a coagulation bath, and is allowed to stand to be fully crosslinked, the standing time is 2-4h, and the defoaming treatment is standing defoaming or vacuum defoaming;

[0017] (5), after the residual coagulation bath on the surface of the fiber is cleaned, the excess water on the surface of the fiber is removed, the fiber is frozen, the fiber is taken out after complete freezing, and the intelligent conductive fiber with a skin-core structure is obtained through freeze drying in a freeze dryer, the freezing time is 3-5h, and the freeze drying time is 12-24h.

[0018] In the preparation method of the intelligent conductive fiber with a skin-core structure, in step (1), the ratio of the MAX phase to the etchant is 1g:15mL-1g:30mL, the step of preparing a single-layer MXene nanosheet spinning slurry by using oscillation stripping and gradient centrifugal separation is that the accordion-shaped MXene phase is dispersed in water, and then closed oscillation is performed for 15-40min, and then gradient centrifugal separation is performed, the MAX phase is Ti3AlC2 or Ti3C2T x ; the etchant is lithium fluoride (LiF) or hydrochloric acid (HCl), and the concentration of the single-layer MXene nanosheet spinning slurry is 30-70mg / mL.

[0019] In the preparation method of the intelligent conductive fiber with a skin-core structure, in the carbon nanofiber / MXene dispersion liquid, the mass fraction of the single-layer MXene nanosheet is 90-98%, and the mass fraction of the carbon nanofiber is 2-10%.

[0020] In the preparation method of the intelligent conductive fiber with a skin-core structure, in step (3), the solvent is a mixed solution composed of dimethyl sulfoxide, methanol and potassium tert-butoxide, the mass ratio of methanol to potassium tert-butoxide is 1:1, the concentration of the aramid nanofiber spinning solution is 1-2wt%, the nitrogen atom on the aramid amide group is deprotonated in an alkaline environment, macroscopic fiber dispersion is realized, and aramid nanomonomer dispersion liquid in which the nanomonomers exist stably is formed.

[0021] In the preparation method of the intelligent conductive fiber with a skin-core structure, in step (4), the coagulation bath is a 5-10wt% dimethyl sulfoxide aqueous solution, the extrusion speed of the fiber is set to 0.03-0.05mm / s, and the extrusion diameter of the nanofiber is controlled to 1-2mm.

[0022] In the preparation method of the intelligent conductive fiber with a skin-core structure, in step (5), the washing is that the fiber is immersed in ethanol and deionized water for 5-10min, and then taken out, and the process is repeated for 3-5 times.

[0023] The smart conductive fiber with a skin-core structure and the preparation method thereof have the following beneficial effects: in the application, MXene / carbon nanofiber is used as the core layer of the smart conductive fiber. One-dimensional carbon nanofiber and two-dimensional MXene construct a three-dimensional conductive network. The carbon nanofiber has high electrical conductivity, high mechanical strength and nanoscale diameter. The addition of the carbon nanofiber makes the fiber core layer present a “layer support” microstructure, the carbon nanofiber is inserted between the MXene nanosheets, and the problems of wrinkles, disordered structure generated in the assembly process of the MXene nanosheet and weak interfacial force between the layers are improved. The connection between the MXene nanosheets is effectively realized, the MXene nanosheet in the fiber is like a loose skeleton, and the carbon nanofiber is like flexible muscles and tendons connecting and protecting the skeleton. The interaction between the layers is improved, which is helpful for force transmission and promotes efficient transfer of electric charges through the interconnected conductive network. The preparation of the three-dimensional conductive network greatly develops the intrinsic properties of the MXene nanomaterial.

[0024] MXene is used to replace surfactants to realize the dispersion of carbon nanofiber. Carbon nanofiber has unique structure and superior electrical, optical, chemical and thermodynamic properties. Single carbon nanofiber is a fibrous one-dimensional nanomaterial with a large aspect ratio. Therefore, carbon nanofiber is easy to entangle and bond together to form larger agglomerates. The agglomeration effect of nanometer powder and the entanglement and bonding phenomenon of fiber material are combined together, so that the carbon nanofiber agglomerate is more firm, and uniform dispersion is more difficult. Although the traditional surfactant can form non-covalent bond combination with it to obtain non-covalent functionalized carbon nanofiber, and improve the solubility, disperse the carbon nanofiber in the medium, it will greatly reduce the electrical conductivity. MXene has a surfactant-like structure, and the hydrophilic group on the surface has strong adhesion on the surface of the carbon nanofiber, which can overcome the π-π stacking between the carbon nanofibers and realize good dispersion of the carbon nanofibers without weakening the electrical conductivity.

[0025] A functional material and a skeleton material are combined, and aramid nanofiber is used as a functional material to protect the core layer. Aramid nanofiber is a new type of polymer nanofiber, which not only retains the structural characteristics and excellent mechanical properties and thermal stability of macro aramid fiber, but also has new connotation and excellent properties due to its unique nanoscale form, so it becomes a potential "reinforcing building unit" for constructing high-performance composite materials, and has attracted great attention in the fields of composite reinforcement and flexible electronics. In terms of structure, the introduction of aramid nanofiber does not hinder the complete electron transfer channel, and the design of the separation layer ensures excellent performance. At the same time, the surface of MXene has rich hydroxyl groups, and the structural homology provides hydrogen bonds, which further ensures the stable interface bonding between the skin layer and the core layer. Aramid nanofiber as a protective layer completely wraps the core layer, so as to isolate it from the external environment and avoid oxidation. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 Figure 1 is an electron microscope image of the surface micro-morphology of the MXene / carbon nanofiber@aramid nanofiber intelligent conductive fiber;

[0027] Figure 2 Figure 2 is an electron microscope image of the cross-sectional micro-morphology of the MXene / carbon nanofiber@aramid nanofiber intelligent conductive fiber;

[0028] Figure 3 Figure 3 is a photograph of the MXene / carbon nanofiber@aramid nanofiber intelligent conductive fiber;

[0029] Figure 4 Figure 4 is an electron microscope image of the three-dimensional network conductive layer micro-morphology of the MXene / carbon nanofiber@aramid nanofiber intelligent conductive fiber. DETAILED DESCRIPTION

[0030] The application will be described in detail below in combination with the drawings and specific embodiments.

[0031] An intelligent conductive fiber with a skin-core structure is prepared by coaxial spinning of a carbon nanofiber / MXene dispersion liquid prepared from a single-layer MXene nanosheet spinning slurry and carbon nanofiber, and an aramid nanofiber monomer dispersion liquid prepared from aramid nanofiber and a solvent. In the carbon nanofiber / MXene dispersion liquid, MXene disperses the carbon nanofiber. The skin layer of the intelligent conductive fiber is aramid nanofiber, and the core layer is a three-dimensional conductive network constructed by two-dimensional MXene nanosheets and one-dimensional carbon nanomaterials interspersed between the two-dimensional MXene nanosheets and connecting the two-dimensional MXene nanosheets. The core layer presents a "layer support" microstructure.

[0032] The intelligent conductive fiber with a skin-core structure described above, wherein the aramid nanofiber is para-aramid, and the length is 5-10 mm.

[0033] The smart conductive fiber with the core-sheath structure has an electrical conductivity of 1.42-2.12 x 10 5 S / m, a breaking strength of 197-285 MPa, and an elongation at break of 10%-12%.

[0034] The smart conductive fiber with the core-sheath structure has a diameter of 1-2 mm.

[0035] Example 1

[0036] The method for preparing the smart conductive fiber with the core-sheath structure includes the following steps:

[0037] (1) chemically etching raw material MAX phase through an etchant, reacting under heating conditions, and preparing single-layer MXene nanosheet spinning slurry through steps of washing, oscillation stripping, and gradient centrifugal separation;

[0038] (2) diluting the single-layer MXene nanosheet spinning slurry with deionized water to 30 mg / mL -1 , to form a carbon nanofiber / MXene dispersion liquid with single-layer MXene nanosheets and carbon nanofibers; the stirring reaction time is 1 h, and the ultrasonic time is 30 min; in the carbon nanofiber / MXene dispersion liquid, the mass fraction of the single-layer MXene nanosheets is 80%, and the mass fraction of the carbon nanofibers is 20%;

[0039] (3) adding para-aramid fiber to a solvent and reacting under magnetic stirring conditions to form a uniform dispersion liquid of aramid nanofibers;

[0040] (4) defoaming the solutions obtained in steps (2) and (3), respectively, adding the solutions into syringes, connecting the syringes to coaxial needles, and simultaneously injecting the solutions into a coagulation bath to form fibers, allowing the fibers to fully crosslink by standing for 2 h, and defoaming by standing defoaming or vacuum defoaming;

[0041] (5) after cleaning residual coagulation bath on the surface of the fibers, removing excess water on the surface of the fibers, freezing the fibers, taking out the fibers after complete freezing, and obtaining the smart conductive fiber with the core-sheath structure through freeze-drying in a freeze dryer; the freezing time is 3 h, and the freeze-drying time is 12 h.

[0042] In the above-mentioned method for preparing intelligent conductive fibers with a core-sheath structure, in step (1), the ratio of MAX phase to etchant is 1g:15mL. The step of preparing a single-layer MXene nanosheet spinning slurry using oscillation exfoliation and gradient centrifugation involves dispersing the accordion-shaped MXene phase in water, followed by closed oscillation for 15 minutes, and then gradient centrifugation. The MAX phase is Ti3AlC2 or Ti3C2T. x The etching agent is lithium fluoride (LiF) or hydrochloric acid (HCl), and the concentration of the monolayer MXene nanosheet spinning slurry is 30 mg / mL.

[0043] In the above-mentioned method for preparing intelligent conductive fibers with a core-sheath structure, in step (3), the solvent is a mixed solution composed of dimethyl sulfoxide, methanol, and potassium tert-butoxide, wherein the mass ratio of methanol to potassium tert-butoxide is 1:1, the concentration of the aramid nanofiber spinning solution is 1 wt%, and in an alkaline environment, the nitrogen atoms on the para-aramid amide groups are deprotonated to achieve macroscopic fiber dispersion, forming a nanomonomer and a stable aramid nanomonomer dispersion.

[0044] In the above-mentioned method for preparing intelligent conductive fibers with a core-sheath structure, in step (4), the coagulation bath is a 5wt% dimethyl sulfoxide aqueous solution, the fiber extrusion speed is set to 0.03mm / s, and the extrusion diameter of the nanofiber is controlled to 1mm.

[0045] In the above-mentioned method for preparing intelligent conductive fibers with a core-sheath structure, step (5) involves washing the fibers by immersing them in ethanol and deionized water for 5 minutes each, then removing them and repeating this process three times.

[0046] Example 2

[0047] The similarities between this embodiment and Embodiment 1 will not be repeated here. The difference lies in the following steps: A method for preparing a smart conductive fiber with a core-sheath structure includes the following steps:

[0048] (1) The raw material MAX phase was chemically etched by an etchant, reacted under heating conditions, and then prepared into a single-layer MXene nanosheet spinning slurry through washing, oscillation peeling and gradient centrifugation.

[0049] (2) Dilute the single-layer MXene nanosheet spinning sizing agent with deionized water to 40 mg / mL. -1 A carbon nanofiber / MXene dispersion with monolayer MXene nanosheets and carbon nanofibers was formed; the stirring reaction time was 1.5 h and the ultrasonic time was 40 min; in the carbon nanofiber / MXene dispersion, the mass fraction of monolayer MXene nanosheets was 98% and the mass fraction of carbon nanofibers was 2%.

[0050] (3) adding para-aramid into the solvent, reacting under the condition of magnetic stirring to form a uniform dispersion solution of aramid nanofiber;

[0051] (4) after defoaming treatment of the solutions obtained in steps (2) and (3), respectively adding the solutions into syringes, connecting the syringes to coaxial needles, and simultaneously injecting into a coagulation bath to form fibers, and standing to allow the fibers to be fully crosslinked, the standing time being 3 h, and the defoaming treatment being standing defoaming or vacuum defoaming;

[0052] (5) after cleaning the coagulation bath remaining on the surface of the fibers, removing the excess water on the surface of the fibers, freezing the fibers, taking out the fibers after thorough freezing, and freeze-drying the fibers in a freeze-drying machine to obtain the smart conductive fiber with a skin-core structure, the freezing time being 4 h, and the freeze-drying time being 18 h.

[0053] In the step (1) of the above method for preparing the smart conductive fiber with a skin-core structure, the ratio of the MAX phase to the etchant is 1 g:20 mL, the step of preparing a single-layer MXene nanosheet spinning solution by using the oscillation peeling and gradient centrifugal separation is to disperse the accordion-shaped MXene phase in water, perform closed oscillation for 30 min, and then perform gradient centrifugal separation, and the concentration of the single-layer MXene nanosheet spinning solution is 50 mg / mL.

[0054] In the step (3) of the above method for preparing the smart conductive fiber with a skin-core structure, the solvent is a mixed solution composed of dimethyl sulfoxide, methanol, and potassium tert-butoxide, the mass ratio of the methanol to the potassium tert-butoxide is 1:1, the concentration of the aramid nanofiber spinning solution is 1.5 wt%, the nitrogen atom on the para-aramid amide group is deprotonated in an alkaline environment to realize the dispersion of the macroscopic fiber, and the aramid nanomonomer dispersion solution is formed and the aramid nanomonomer stably exists.

[0055] In the step (4) of the above method for preparing the smart conductive fiber with a skin-core structure, the coagulation bath is an 8 wt% dimethyl sulfoxide aqueous solution, the extrusion speed of the fiber is set to 0.04 mm / s, and the extrusion diameter of the nanofiber is controlled to 1.5 mm.

[0056] In the step (5) of the above method for preparing the smart conductive fiber with a skin-core structure, the washing is to immerse the fiber in ethanol and deionized water for 8 min respectively, and then take out the fiber, and repeat the above steps for 4 times.

[0057] Example 3

[0058] The same as example 1, the difference is that the method for preparing the smart conductive fiber with a skin-core structure comprises the following steps:

[0059] (1), the raw material MAX phase is chemically etched by an etchant, and is reacted under heating conditions, and is prepared into a single-layer MXene nanosheet spinning slurry through washing, oscillation peeling and gradient centrifugal separation steps;

[0060] (2), the single-layer MXene nanosheet spinning slurry is diluted with deionized water to 50mg / mL -1 , to form a carbon nanofiber / MXene dispersion liquid with single-layer MXene nanosheets and carbon nanofibers; the stirring reaction time is 2h, and the ultrasonic time is 60min; the mass fraction of the single-layer MXene nanosheets in the carbon nanofiber / MXene dispersion liquid is 99%, and the mass fraction of the carbon nanofibers is 1%;

[0061] (3), para-aramid is added to a solvent, and a uniform dispersion liquid of aramid nanofibers is formed under magnetic stirring conditions;

[0062] (4), the solutions obtained in steps (2) and (3) are defoamed and then added into syringes, the syringes are connected to coaxial needles, and the syringes are injected into a coagulation bath at the same time to form fibers, which are crosslinked by standing for 4h, and the defoaming treatment is standing defoaming or vacuum defoaming;

[0063] (5), after cleaning the residual coagulation bath on the surface of the fibers, the excess water on the surface of the fibers is removed, the fibers are frozen, and the fibers are taken out after complete freezing, and a smart conductive fiber with a skin-core structure is obtained by freeze-drying in a freeze dryer, the freezing time is 5h, and the freeze-drying time is 24h.

[0064] The preparation method of the smart conductive fiber with a skin-core structure, in step (1), the ratio of the MAX phase to the etchant is 1g:30mL, and the step of preparing the single-layer MXene nanosheet spinning slurry by using the oscillation peeling and gradient centrifugal separation steps is to disperse the concertina-shaped MXene phase in water, and then to perform closed oscillation for 40min and gradient centrifugal separation; the MAX phase is Ti3AlC2 or Ti3C2T x ; the etchant is lithium fluoride (LiF) or hydrochloric acid (HCl), and the concentration of the single-layer MXene nanosheet spinning slurry is 70mg / mL.

[0065] The preparation method of the smart conductive fiber with a skin-core structure, in step (3), the solvent is a mixed solution composed of dimethyl sulfoxide, methanol and potassium tert-butoxide, the mass ratio of methanol to potassium tert-butoxide is 1:1, the concentration of the aramid nanofiber spinning solution is 2wt%, the nitrogen atoms on the para-aramid amide groups are deprotonated in an alkaline environment, the macroscopic fibers are dispersed, and an aramid nanomonomer dispersion liquid in which the aramid nanomonomers are stably present is formed.

[0066] The preparation method of the smart conductive fiber with a skin-core structure, in the step (4), the coagulation bath is 10wt% dimethyl sulfoxide aqueous solution, the extrusion speed of the fiber is set to 0.05mm / s, and the extrusion diameter of the nanofiber is controlled to 2mm.

[0067] The preparation method of the smart conductive fiber with a skin-core structure, in the step (5), the washing is that the fiber is immersed in ethanol and deionized water for 10min respectively, and then taken out, and the above steps are repeated for 5 times.

[0068] Example 4

[0069] The preparation method of the smart conductive fiber with a skin-core structure, in the step (4), the coagulation bath is 10wt% dimethyl sulfoxide aqueous solution, the extrusion speed of the fiber is set to 0.05mm / s, and the extrusion diameter of the nanofiber is controlled to 2mm.

[0070] (1) The raw material MAX phase is chemically etched by etchant, reacted under heating conditions, and prepared into single-layer MXene nanosheet spinning slurry through washing, oscillation stripping and centrifugal separation steps. The specific operation is as follows: 1g Ti3AlC2 MAX phase powder is slowly added to the etching solution composed of 20ml 9M HCl and 1.6g LiF, and stirred at 50℃ constant temperature for 30h. The obtained dispersion liquid is centrifuged at 6000rpm for 10min, and washed with deionized water, and repeated for several cycles until the supernatant pH is about 7. Then the self-layered MXene nanosheet is collected as supernatant, and centrifuged at 1500rpm for 30min. The dark green supernatant is further centrifuged at 10000rpm for 60min, and the precipitate containing thin sheets is collected.

[0071] (2) After measuring the concentration of the deposit obtained in step (1), the MXene deposit is diluted to 50mg mL -1 , 0.1g carbon nanofiber is added to the single-layer MXene nanosheet water dispersion liquid obtained in step (1), mixed and stirred for 1h, and then ultrasonically treated for 40min to obtain a spinning liquid in which single-layer MXene nanosheet and carbon nanofiber are uniformly dispersed;

[0072] (3) The para-aramid (poly-p-phenylene terephthalamide) is added to a mixed solution composed of dimethyl sulfoxide, methanol and potassium tert-butoxide, the nitrogen atoms on the amide groups of the para-aramid fiber are deprotonated in an alkaline environment, the macroscopic fiber is dispersed, and the aramid nanomonomer dispersion liquid in which the nanomonomer stably exists is formed, that is, the aramid nanofiber dispersion liquid. The specific operation is as follows: 0.45g para-aramid fiber and equal amount of methanol and potassium tert-butoxide are added to a beaker containing 40ml dimethyl sulfoxide, and stirred magnetically at room temperature for 4h to obtain 1wt% aramid nanofiber dispersion liquid;

[0073] (4) The solutions obtained in steps (2) and (3) are vacuum defoaming treated, then are respectively added into syringes, the syringes are connected to 22G / 17G coaxial needles, and are injected into 10wt% dimethyl sulfoxide aqueous solution at an extrusion speed of 0.03mm / s, and are left to stand for 2h to make them fully crosslinked;

[0074] (5) The coagulation bath fibers remaining on the fiber surface are sequentially soaked in ethanol and deionized water for 5-10min, and are taken out, and the operation is repeated for 3-5 times, the fibers are cleaned, the excess water on the fiber surface is removed, the fibers are placed in an ultra-low temperature refrigerator and frozen for 5h, and after being completely frozen, the fibers are taken out, and are freeze-dried in a freeze dryer for 24h to obtain the smart conductive fiber with a skin-core structure.

[0075] The smart conductive fiber with a skin-core structure prepared in the embodiment has an electrical conductivity of 1.42x10 5 S / m, a breaking strength of 197MPa, and an elongation at break of 10%.

[0076] Example 5

[0077] The same as the embodiment 1, the difference is that the preparation method of the smart conductive fiber with a skin-core structure comprises the following steps:

[0078] (1) The raw material MAX phase is chemically etched by an etchant, and is reacted under heating conditions, and is prepared into a single-layer MXene nanosheet spinning slurry through the steps of washing, oscillation stripping and centrifugal separation. The specific operation is as follows: 1g of Ti3AlC2 MAX phase powder is slowly added into an etching liquid composed of 20mL of 9M HCl and 1.6g of LiF, and is stirred under the condition of 50℃ constant temperature for 30h. The obtained dispersion liquid is centrifuged at 6000rpm for 10min, and is washed with deionized water, and the operation is repeated for several cycles until the pH of the supernatant is about 7. Then the self-layered MXene nanosheet is collected as the supernatant, and is centrifuged at 1500rpm for 30min. The dark green supernatant is further centrifuged at 10000rpm for 60min, and the precipitate containing thin sheets is collected.

[0079] (2) After measuring the concentration of the deposit obtained in step (1), the MXene deposit is diluted to 50mg mL -1

[0080] ​(3) Para-aramid (poly(p-phenylene terephthalamide)) was added to a mixed solution composed of dimethyl sulfoxide, methanol, and potassium tert-butoxide. Under alkaline conditions, the nitrogen atoms on the amide groups of the para-aramid fibers were deprotonated to achieve macroscopic fiber dispersion, forming a stable aramid nanomonomer dispersion, i.e., an aramid nanofiber dispersion. Specifically, 0.45 g of para-aramid fiber was added to a beaker containing 40 ml of dimethyl sulfoxide along with equal amounts of methanol and potassium tert-butoxide. The mixture was magnetically stirred at room temperature for 4 h to obtain a 1 wt% aramid nanofiber dispersion.

[0081] (4) After vacuum defoaming the solutions obtained in steps (2) and (3), add them into the syringes respectively, connect the syringes to the 22G / 17G coaxial needles, and inject them into 10wt% dimethyl sulfoxide aqueous solution at an extrusion speed of 0.03mm / s. Let them stand for 2h to allow them to fully crosslink.

[0082] (5) Soak the fiber with residual coagulation bath on the fiber surface in ethanol and deionized water for 5-10 minutes each, then take it out and repeat 3-5 times. After cleaning, remove excess water from the fiber surface and put it in an ultra-low temperature freezer to freeze for 5 hours. After freezing completely, take it out and freeze-dry it in a freeze dryer for 24 hours to obtain a smart conductive fiber with a core-sheath structure.

[0083] The smart conductive fiber with a core-sheath structure prepared in this embodiment has a conductivity of 1.58 × 10⁻⁶. 5 S / m, breaking strength: 222MPa, breaking elongation: 10.5%.

[0084] Example 6

[0085] The similarities between this embodiment and Embodiment 1 will not be repeated here. The difference lies in the following steps: A method for preparing a smart conductive fiber with a core-sheath structure includes the following steps:

[0086] (1) The raw material MAX phase was chemically etched with an etchant, reacted under heating conditions, and then washed, shaken and peeled off, and centrifuged to prepare a single-layer MXene nanosheet spinning slurry. Specifically, 1g of Ti3AlC2 MAX phase powder was slowly added to an etching solution consisting of 20mL of 9M HCl and 1.6g of LiF, and stirred at 50℃ for 30h. The resulting dispersion was centrifuged at 6000rpm for 10min and washed with deionized water, repeating several cycles until the pH of the supernatant reached approximately 7. The self-stratified MXene nanosheets were then collected as the supernatant and centrifuged at 1500rpm for 30min. The dark green supernatant was further centrifuged at 10000rpm for 60min, and the precipitate containing the flakes was collected.

[0087] (2) After measuring the concentration of the deposit obtained in step (1), dilute the MXene deposit with deionized water to 50 mg / mL -1 Add 0.06 g of carbon nanofibers to the monolayer MXene nanosheet water dispersion obtained in step (1), mix and stir for 1 h, and then ultrasonic for 40 min to obtain a spinning solution in which monolayer MXene nanosheets and carbon nanofibers are uniformly dispersed.

[0088] (3) Add para-aramid (poly-p-phenyleneterephthalamide) to a mixed solution composed of dimethyl sulfoxide, methanol, and potassium tert-butoxide, deprotonate the nitrogen atoms on the amide groups of the para-aramid fibers in an alkaline environment, realize the dispersion of macroscopic fibers, and form aramid nanofiber dispersion liquid in which aramid nanomonomers stably exist. The specific operation is as follows: add 0.45 g of para-aramid fibers and equal amounts of methanol and potassium tert-butoxide to a beaker containing 40 ml of dimethyl sulfoxide, and magnetically stir at room temperature for 4 h to obtain 1 wt% aramid nanofiber dispersion liquid;

[0089] (4) After vacuum defoaming treatment of the solutions obtained in steps (2) and (3), respectively inject them into a 10 wt% dimethyl sulfoxide aqueous solution at an extrusion speed of 0.03 mm / s using a 22G / 17G coaxial needle, and let stand for 2 h to allow sufficient crosslinking;

[0090] (5) Place the residual coagulation bath fibers on the fiber surface in ethanol and deionized water for 5-10 min, respectively, then take them out, repeat 3-5 times, clean them, remove the excess water on the fiber surface, place them in an ultra-low temperature freezer for 5 h, take them out after complete freezing, and freeze dry them in a freeze dryer for 24 h to obtain a smart conductive fiber with a skin-core structure.

[0091] The smart conductive fiber with a skin-core structure prepared in this example has an electrical conductivity of 1.74 x 10 5 S / m, a breaking strength of 245 MPa, and an elongation at break of 10.9%.

[0092] Example 7

[0093] This example is the same as example 1, and the differences are as follows: a method for preparing a smart conductive fiber with a skin-core structure, comprising the following steps:

[0094] A method for preparing a smart conductive fiber with a skin-core structure, comprising the following steps:

[0095] (1) The raw material MAX phase was chemically etched with an etchant, reacted under heating conditions, and then washed, shaken and peeled off, and centrifuged to prepare a single-layer MXene nanosheet spinning slurry. Specifically, 1g of Ti3AlC2 MAX phase powder was slowly added to an etching solution consisting of 20mL of 9M HCl and 1.6g of LiF, and stirred at 50℃ for 30h. The resulting dispersion was centrifuged at 6000rpm for 10min and washed with deionized water, repeating several cycles until the pH of the supernatant reached approximately 7. The self-stratified MXene nanosheets were then collected as the supernatant and centrifuged at 1500rpm for 30min. The dark green supernatant was further centrifuged at 10000rpm for 60min, and the precipitate containing the flakes was collected.

[0096] (2) After measuring the sediment concentration obtained in step (1), dilute the MXene sediment to 50 mg / mL with deionized water. -1 , , 0.04g of carbon nanofibers were added to the aqueous dispersion of monolayer MXene nanosheets obtained in step (1), and after mixing and stirring for 1h, the mixture was sonicated for 40min to obtain a spinning solution in which monolayer MXene nanosheets and carbon nanofibers were uniformly dispersed.

[0097] (3) Para-aramid (poly(p-phenylene terephthalamide)) was added to a mixed solution composed of dimethyl sulfoxide, methanol, and potassium tert-butoxide. Under alkaline conditions, the nitrogen atoms on the amide groups of the para-aramid fibers were deprotonated to achieve macroscopic fiber dispersion, forming a stable aramid nanomonomer dispersion, i.e., an aramid nanofiber dispersion. Specifically, 0.45 g of para-aramid fiber was added to a beaker containing 40 ml of dimethyl sulfoxide along with equal amounts of methanol and potassium tert-butoxide. The mixture was magnetically stirred at room temperature for 4 h to obtain a 1 wt% aramid nanofiber dispersion.

[0098] (4) After vacuum defoaming the solutions obtained in steps (2) and (3), add them into the syringes respectively, connect the syringes to the 22G / 17G coaxial needles, and inject them into 10wt% dimethyl sulfoxide aqueous solution at an extrusion speed of 0.03mm / s. Let them stand for 2h to allow them to fully crosslink.

[0099] (5) Soak the fiber with residual coagulation bath on the fiber surface in ethanol and deionized water for 5-10 minutes each, then take it out and repeat 3-5 times. After cleaning, remove excess water from the fiber surface and put it in an ultra-low temperature freezer to freeze for 5 hours. After freezing completely, take it out and freeze-dry it in a freeze dryer for 24 hours to obtain a smart conductive fiber with a core-sheath structure.

[0100] The smart conductive fiber with a core-sheath structure prepared in this embodiment has an electrical conductivity of 1.91 × 10⁻⁶. 5S / m, breaking strength: 268 MPa, elongation at break: 11.4%.

[0101] Example 8

[0102] The same as example 1, the difference is that: a preparation method of a smart conductive fiber with a skin-core structure, comprising the following steps:

[0103] A preparation method of a smart conductive fiber with a skin-core structure, comprising the following steps:

[0104] (1) The raw material MAX phase is chemically etched by etchant, and reacts under heating conditions, and is prepared into a single-layer MXene nanosheet spinning slurry through washing, oscillation stripping and centrifugal separation steps. The specific operation is: 1g Ti3AlC2 MAX phase powder is slowly added to the etching solution composed of 20ml 9M HCl and 1.6g LiF, and stirred at 50℃ constant temperature for 30h. The obtained dispersion liquid is centrifuged at 6000rpm for 10min, and washed with deionized water, and repeated for several cycles until the supernatant pH is about 7. Then the self-layered MXene nanosheet is collected as supernatant, and centrifuged at 1500rpm for 30min. The dark green supernatant is further centrifuged at 10000rpm for 60min, and the precipitate containing thin sheets is collected.

[0105] (2) After measuring the sediment concentration, the MXene sediment is diluted to 50mg mL -1 0.02g carbon nanofiber is added to the single-layer MXene nanosheet water dispersion liquid obtained in step (1), mixed and stirred for 1h, and then ultrasonically treated for 40min to obtain a spinning liquid in which single-layer MXene nanosheets and carbon nanofibers are uniformly dispersed;

[0106] (3) Para-aramid (poly-p-phenylene terephthalamide) is added to a mixed solution composed of dimethyl sulfoxide, methanol and potassium tert-butoxide, and the nitrogen atoms on the amide groups of the para-aramid fiber are deprotonated in an alkaline environment to realize the dispersion of macroscopic fibers and form aramid nanomonomer dispersion liquid, i.e. aramid nanofiber dispersion liquid. The specific operation is: 0.45g para-aramid fiber and equal amount of methanol and potassium tert-butoxide are added to a beaker containing 40ml dimethyl sulfoxide, and magnetic stirring is carried out at room temperature for 4h to obtain 1wt% aramid nanofiber dispersion liquid;

[0107] (4) The solutions obtained in steps (2) and (3) are vacuum defoaming treated, and then added into syringes respectively, the syringes are connected to 22G / 17G coaxial needles, and injected into 10wt% dimethyl sulfoxide aqueous solution at an extrusion speed of 0.03mm / s, and left to stand for 2h to make it crosslinking fully;

[0108] (5) The fiber surface residual coagulation bath fiber is placed in ethanol and deionized water in turn for 5-10 min, and then taken out. The above steps are repeated for 3-5 times. After cleaning, the fiber surface is removed from the water, and then placed in an ultra-low temperature refrigerator for 5 h. After being completely frozen, the fiber is taken out and dried in a freeze dryer for 24 h to obtain the smart conductive fiber with a skin-core structure.

[0109] The smart conductive fiber with a skin-core structure prepared in the embodiment has an electrical conductivity of 2.12×10 5 S / m, a breaking strength of 285 MPa, and an elongation at break of 12%.

[0110] Of course, the above description is not a limitation of the present application, and the present application is not limited to the above examples. Changes, modifications, additions or substitutions made by ordinary skilled in the art within the scope of the present application should also be within the scope of the present application.

Claims

1. A smart conductive fiber with a core-sheath structure, characterized in that: The intelligent conductive fiber is prepared by coaxial spinning of a carbon nanofiber / MXene dispersion made from a single-layer MXene nanosheet spinning slurry and carbon nanofibers, and an aramid nanomonomer dispersion made from aramid nanofibers and a solvent. In the carbon nanofiber / MXene dispersion, MXene disperses the carbon nanofibers. The outer layer of the intelligent conductive fiber is aramid nanofibers, and the core layer is a three-dimensional conductive network constructed from two-dimensional MXene nanosheets and one-dimensional carbon nanomaterials interspersed between and connecting the two-dimensional MXene nanosheets. The core layer exhibits a "layer-supported" microstructure. Its preparation method includes the following steps: (1) The raw material MAX phase is chemically etched by an etchant, reacted under heating conditions, and then prepared into a single-layer MXene nanosheet spinning slurry through washing, oscillation peeling and gradient centrifugation. (2) The monolayer MXene nanosheet spinning slurry is diluted with deionized water to 30-50 mgmL−1, and then mixed and stirred with carbon nanofibers, followed by an ultrasonic step, to form a carbon nanofiber / MXene dispersion containing monolayer MXene nanosheets and carbon nanofibers; the stirring reaction time is 1-2 h, and the ultrasonic time is 30-60 min; in the carbon nanofiber / MXene dispersion, the mass fraction of monolayer MXene nanosheets is 80-99%, and the mass fraction of carbon nanofibers is 1-20%. (3) Para-aramid is added to a solvent and reacted under magnetic stirring to form an aramid nanomonomer dispersion; the solvent is a mixed solution composed of dimethyl sulfoxide, methanol, and potassium tert-butoxide, wherein the mass ratio of methanol to potassium tert-butoxide is 1:1, and the concentration of the aramid nanomonomer dispersion is 1-2 wt%. (4) After defoaming the dispersions obtained in steps (2) and (3), add them into syringes, connect the syringes to the coaxial needles, and inject them into the coagulation bath to form fibers. Let them stand to allow them to fully crosslink. The standing time is 2-4 hours. The defoaming treatment is either standing defoaming or vacuum defoaming. (5) After cleaning the coagulation bath residue on the fiber surface, remove excess water from the fiber surface, freeze the fiber, take it out after it is completely frozen, and freeze-dry it in a freeze dryer to obtain intelligent conductive fiber with a core-sheath structure. The freezing time is 3-5 hours and the freeze-drying time is 12-24 hours.

2. The intelligent conductive fiber with a core-sheath structure according to claim 1, characterized in that, The aramid nanofibers are 5-10 mm in length.

3. The intelligent conductive fiber with a core-sheath structure according to claim 2, characterized in that, The diameter of the intelligent conductive fiber is 1-2 mm.

4. The intelligent conductive fiber with a core-sheath structure according to claim 3, characterized in that, The electrical conductivity of the intelligent conductive fiber is: 1.42-2.12×10⁻⁶. 5 S / m, breaking strength: 197-285MPa, breaking elongation: 10%-12%.

5. The intelligent conductive fiber with a core-sheath structure according to claim 1, characterized in that, In step (1), the ratio of the MAX phase to the etchant is 1g:15mL-1g:30mL. The step of preparing the monolayer MXene nanosheet spinning slurry by oscillation peeling and gradient centrifugation is as follows: the accordion-shaped MXene phase is dispersed in water, oscillated in a closed environment for 15-40 min, and then separated by gradient centrifugation; the MAX phase is Ti3AlC2; the etchant is lithium fluoride or hydrochloric acid; and the concentration of the monolayer MXene nanosheet spinning slurry is 30-70mg / mL.

6. The intelligent conductive fiber with a core-sheath structure according to claim 5, characterized in that, In the carbon nanofiber / MXene dispersion, the mass fraction of monolayer MXene nanosheets is 90-98%, and the mass fraction of carbon nanofibers is 2-10%.

7. The intelligent conductive fiber with a core-sheath structure according to claim 1, characterized in that, In step (4), the coagulation bath is a 5-10 wt% dimethyl sulfoxide aqueous solution, the fiber extrusion speed is set to 0.03-0.05 mm / s, and the fiber extrusion diameter is controlled to be 1-2 mm.

8. The intelligent conductive fiber with a core-sheath structure according to claim 7, characterized in that, In step (5), the washing process involves immersing the fibers in ethanol and deionized water for 5-10 minutes each, then removing them and repeating this process 3-5 times.

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