Beiconn can provide coaxial wet spinning to prepare ANF@MXene core-shell fibers (customizable)

With the development of wearable electronic devices, conductive, high-strength and extreme-environment-resistant fibers have important research value. Transition metal carbon/nitride (MXene) has both high conductivity and hydrophilic properties, and is more suitable for preparing conductive fibers than traditional carbon nanomaterials. However, the key issues affecting the development of MXene-based conductive fibers are the poor spinnability of MXene suspensions and the low mechanical properties of fibers. At the same time, the easy oxidation of MXene is also a disadvantage. To this end, we prepared an ANF@MXene core with super toughness, high strength, high conductivity and environmental stability by using a coaxial wet spinning method with conductive MXene as the core layer and aramid nanofiber (ANF) as the shell layer. shell fibers. The high-performance ANF shell plays an important role in enhancing MXene spinnability and enhancing the mechanical properties and environmental stability of MXene-based fibers. The highly oriented ANF@MXene core-shell fibers solve the problem that MXene fibers cannot have both electrical conductivity and high mechanical properties, and take into account high electrical conductivity, super toughness, high tensile strength and environmental stability.
Super-Tough and Environmentally Stable Aramid Nanofiber@MXene Coaxial Fibers with Outstanding Electromagnetic Interference Shielding Efficiency

Liu-Xin Liu, Wei Chen, Hao-Bin Zhang*, Lvxuan Ye, Zhenguo Wang, Yu Zhang,Peng Min, and Zhong-Zhen Yu*

Nano-Micro Letters (2022) 14: 111

https://doi.org/10.1007/s40820-022-00853-1



Highlights of this article

1. Ultra-tough and high-strength ANF@MXene core-shell fibers were prepared by coaxial wet spinning.

2. The toughness of the core-shell fibers is as high as 48.1 MJ m⁻3, and the tensile strength is 502.9 MPa.
3. ANF@MXene fibers have excellent chemical stability under extreme environmental conditions.
brief introduction

Although MXene materials have both high electrical conductivity and hydrophilicity, and have good application prospects in the field of multifunctional fibers and fabrics, it is difficult to simultaneously improve the electrical conductivity of MXene fibers due to the insufficient rigidity and interlayer force of MXene nanosheets. mechanical properties. To this end, we prepared core-shell fibers with MXene as the core and aramid nanofiber (ANF) as the shell with high conductivity, super toughness, high strength and good environmental stability by core-shell wet spinning. The high orientation and low defect structure of the fibers result in super toughness of 48.1 MJ m⁻3, high strength of 502.9 MPa, and high electrical conductivity of 3.0 x10⁵ S m⁻1. The ultra-tough and conductive ANF@MXene core-shell fibers can be woven into fabrics with an electromagnetic shielding effectiveness of 83.4 dB at a thickness of 213 μm. The protective effect of the ANF shell also endows the fibers with satisfactory cyclic stability and resistance to acids, alkalis, seawater, and high and low temperatures under dynamic tensile and flexural deformations. Core-shell fibers also have excellent antioxidant properties. Multifunctional core-shell fibers have promising development prospects in the fields of electromagnetic shielding fabrics, wearable electronic devices, and aerospace.

Graphical guide

I Coaxial wet spinning to prepare ANF@MXene core-shell fibers
It is of great significance to greatly improve the toughness and tensile strength of MXene fibers on the premise of retaining the electrical conductivity of MXene materials. As shown in Fig. 1a,b, the coaxial wet spinning method was adopted, using ANF as the shell layer spinning solution and MXene as the core layer spinning solution, under fluid drafting, high orientation, super toughness, high strength and high Conductive ANF@M core-shell fibers, in which the protonation of water on ANF in the coagulation bath of ammonium chloride aqueous phase, the cross-linking effect of ammonium ions on MXene, and the hydrogen bonding between MXene and ANF are beneficial to improve the mechanical properties of fibers . The orientation properties of pure MXene fibers and ANF@M fibers under different spinning conditions were characterized by small-angle X-ray scattering and wide-angle X-ray scattering (Fig. 1c–e), where the draft ratio of pure MXene fibers was set as 1.1 and the concentration of 50 mg mL⁻1. The results show that ANF@M fibers have a higher degree of orientation than pure MXene fibers under the same spinning conditions. The ANF shell is equivalent to the confinement channel in microfluidic spinning, and the MXene spinning solution has stronger orienting ability and higher degree of orientation under the confinement of the ANF shell.



Figure 1. (a) ANF@M core-shell fibers prepared by coaxial wet spinning; (b) ANF protonation process and its interfacial interaction with MXene; (c) MXene fibers and (d,e) ANF@M (c1, d1, e1) cross-section SEM image, (c2, d2, e2) SAXS image and (c3, d3, e3) WAXS image of the fiber.

II Mechanical properties and fracture behavior of ANF@MXene core-shell fibers

It can be seen from Figure 2a,b that the tensile strength and toughness of ANF@M fibers are greatly improved compared with pure MXene fibers. At the same time, reducing the concentration of the MXene core layer further improved the mechanical properties of the core-shell fibers. The tough ANF@M fibers can be tied into dead knots and can support a 100 g weight in a circular motion (Fig. 2c). The crimped shape of the MXene sheet in the SEM image of the fractured ANF@M fiber indicates the ductile fracture of MXene, and the oriented ANF microfiber clusters are also beneficial to improve the fiber toughness. Furthermore, the interfacial bonding was enhanced by hydrogen bonding between MXene and ANF (Fig. 2d–i). Figure 2j visualizes the process of fiber ductile fracture.

Figure 2. Comparison of (a) stress-strain curves, (b) tensile strength, and toughness of MXene fibers and ANF@M fibers; (c) SEM image of ANF@M fibers tied into knots, single ANF The @M fiber supports a 100 g weight in a circular motion. The white scale in the figure is 1 mm; (d, g) fracture surface of ANF@M fiber, (e, f) SEM images of MXene core and (h, i) ANF shell cross-section; (j) ANF@M fiber Diagram of the tensile fracture process.

Conductive and electromagnetic shielding properties of III ANF@MXene core-shell fibers

The ultra-tough and high-strength ANF@M fibers also exhibit excellent electrical conductivity (Fig. 3a). At a draft ratio of 1.1, the conductivity of the ANF@M fibers is about 3 x 10⁵ S m⁻1. In contrast, pure MXene fibers have an electrical conductivity of about 2.1 x 10⁵ S m⁻1 due to their low degree of orientation and imperfect conduction paths. The research results show that the conductive fibers with core-shell structure not only significantly improve the mechanical properties, but also improve the electrical conductivity, providing a method to solve the problem of having both electrical conductivity and mechanical properties in the field of conductive composite fibers through rational structural design. The tough and highly conductive ANF@M fibers have excellent resistance to dynamic tensile fatigue and can be used as wires (Fig. 3b–e). The ANF@M fibers prepared in this work exhibited excellent electrical and mechanical properties (Fig. 3f). The fiber fabric exhibits excellent electromagnetic shielding performance, and the shielding performance remains stable after 5000 cycles of dynamic bending (Fig. 3g, h), and has an absorption-based shielding mechanism (Fig. 3i).




Figure 3. (a) Comparison of electrical conductivity of different fibers; cyclic tensile curves of ANF@M fibers in (b) elastic stage and (c) plastic stage and corresponding (d) resistance changes; (e) single ANF@M fiber M fibers can support 200 g weights and can light up LED lights in a bent state; (f) Comparison of electrical conductivity and mechanical properties of MXene-based fibers; (g) EMI effect of 17-1.1-50M fabrics with hole size and fabric thickness variation graph; (h) EMI shielding curve after bending for 5000 turns; (i) EMI shielding mechanism of ANF@M fabric.

Stability of IV ANF@MXene core-shell fibers under extreme environmental conditions

ANF@M core-shell fibers have excellent antioxidant properties, and can withstand strong acid, strong alkali, water vapor, seawater, as well as high temperature (300 ℃) and low temperature (-196 ℃), non-flammable and non-melting in case of fire (Figure 4) . Its electrical resistance and electromagnetic shielding properties remain basically stable under these extreme environmental conditions, indicating that the lightweight, high-strength, and super-tough ANF@M fibers have good environmental stability and are useful in the fields of aviation, polar workstations, wearable electronics, and artificial intelligence materials. good development prospects.




Figure 4. (a-c) antioxidant properties of ANF@MXene fibers; (d) strong acid and alkali resistance; (e, f) moisture resistance; (g) seawater resistance; (h) high and low temperature resistance and (i) incombustibility.