High-performance electromagnetic interference (EMI) shielding materials with ultraflexibility, outstanding mechanical properties, and superior EMI shielding performances are highly desirable for modern integrated electronic and telecommunication systems in areas such as aerospace, military, artificial intelligence, and smart and wearable electronics. Herein, ultraflexible and mechanically strong aramid nanofiber−Ti 3 C 2 T x MXene/silver nanowire (ANF-MXene/AgNW) nanocomposite papers with double-layered structures are fabricated via the facile two-step vacuum-assisted filtration followed by hot-pressing approach. The resultant doublelayered nanocomposite papers with a low MXene/AgNW content of 20 wt % exhibit an excellent electrical conductivity of 922.0 S•cm −1 , outstanding mechanical properties with a tensile strength of 235.9 MPa and fracture strain of 24.8%, superior EMI shielding effectiveness (EMI SE) of 48.1 dB, and high EMI SE/t of 10 688.9 dB•cm −1 , benefiting from the highly efficient double-layered structures, high-performance ANF substrate, and extensive hydrogen-bonding interactions. Particularly, the nanocomposite papers show a maximum electrical conductivity of 3725.6 S•cm −1 and EMI SE of ∼80 dB at a MXene/AgNW content of 80 wt % with an absorption-dominant shielding mechanism owing to the massive ohmic losses in the highly conductive MXene/AgNW layer, multiple internal reflections between Ti 3 C 2 T x MXene nanosheets and polarization relaxation of localized defects, and abundant terminal groups. Compared with the homogeneously blended ones, the double-layered nanocomposite papers possess greater advantages in electrical, mechanical, and EMI shielding performances. Moreover, the multifunctional double-layered nanocomposite papers exhibit excellent thermal management performances such as high Joule heating temperature at low supplied voltages, rapid response time, sufficient heating stability, and reliability. The results indicate that the double-layered nanocomposite papers have excellent potential for high-performance EMI shielding and thermal management applications in aerospace, military, artificial intelligence, and smart and wearable electronics.

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In order to improve their practical applications, carbon nanotubes (CNTs) have been widely spun into fibers. However, both mechanical strength and electrical conductivity of the CNT fibers are far from the applications. Therefore, a second phase such as polymer has been introduced to increase their strength, but their conductivity further decreases due to the insulating or the low-conductivity action of the incorporated polymer. In this work, we have developed a general and effective route to fabricate CNT/ polymer fibers through the introduction of monomers during an easy solution process followed by an in situ polymerization. The resulting composite fibers show an increased tensile strength and an improved electrical conductivity compared with either the pure CNT fibers or the CNT/polymer fibers prepared by the direct incorporation of polymers. This work demonstrates a fabrication methodology to design and synthesize high-quality CNT/polymer composite materials.

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