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The problem of unstable structure and poor impedance matching of single metal-organic framework (MOF) can be avoided by sintering MOFs and melamine composites to fabricate carbon nanotubes-coated cobalt/carbon nanoparticles (Co@C/CNTs). By regulating the mixing ratio of MOF and melamine, different lengths and amount of carbon nanotubes coated porous cobalt/carbon polyhedrons can be obtained, and the catalytic capability of cobalt can be affected to obtain carbon with different degrees of graphitization. The appropriate ratio can change the dielectric magnetic parameters to optimize the impedance matching of the material. As the result, when the mixing ratio of ZIF-67 and melamine was 1:1, the product Co@C/CNTs/PVDF-1:1 shows the lowest reflection loss (−57.6 dB) at the filling amount of 15 wt% with the thickness of 3.01 mm. The effective absorbing bandwidth (EAB) could achieve 5.4 GHz from 12.6 GHz to 18.0 GHz under the filler loading of 10 wt% with the thickness of 2 mm. These results inaugurate a new avenue for obtaining excellent absorbing composites with lightweight, wide EAB and strong absorbing performance. [Display omitted] • Carbon nanotubes-coated cobalt/carbon nanoparticles (Co@C/CNTs) with excellent performance was successfully synthesized. • An excellent reflection loss (RL) of −57.6 dB with a low filler loading (15 wt%) and thin thickness (3.01 mm). • Effective absorption bandwidth (<−10 dB) can be up to 5.4 GHz under a single thickness (2.00 mm). • The synergistic effect between magnetic components and carbon-based show up good impedance matching. [ABSTRACT FROM AUTHOR]

Modern electronic equipment puts forward stricter requirements for the performance of electromagnetic interference (EMI) shielding materials to cope with the increasingly complex electromagnetic environment. Here, a high-performance polyimide-MXene-multi-wall carbon nanotubes (PI-MXene-MWCNT) nanocomposite films were prepared by a highly controllable electrospinning-spraying process using the design strategy of integrating conductive gradient with the sandwich structure. The top layer and bottom layer of the composite films are PI electrospun fiber films, and the middle layer is composed by MXene and MWCNT. The design strategy of the conductive gradient structure significantly enhances the EMI shielding performance without increasing the filler content, as evidenced by the nanocomposite film's high EMI shielding effectiveness of 66.8 dB and a satisfactory absolute shielding efficiency of 13153.8 dB cm2 g−1. The design strategy of PI sandwich structure endows the nanocomposite film with excellent comprehensive performance. The nanocomposite film not only maintains efficient EMI shielding performance in various extreme conditions, but also has excellent thermal insulation performance (30.5 mW/(m·K)) and flame retardation performance. Meanwhile, the nanocomposite film exhibits good mechanical properties and flexibility, as evidenced by an elongation at break of up to 35.4 %. This work provides inspiration for the preparation of a high-performance EMI shielding material that can be used in extreme environments, which has broad application potential in the field of EMI shielding. A high-performance PI-MXene-MWCNT nanocomposite film that integrates conductive gradient with sandwich structure was prepared using PI as the substrate, MXene as the main filler, and MWCNT as the auxiliary filler. The design strategy of the conductive gradient structure significantly enhances the EMI shielding performance without increasing the filler content, as evidenced by the nanocomposite film's high EMI shielding effectiveness of 66.8 dB. [Display omitted] • The film was prepared by using the design strategy of integrating conductive gradient with sandwich structure. • The film achieves an EMI shielding effectiveness of 66.8 dB, and SSE/t of the film reached a satisfying 13153.8 dB cm2 g−1. • The film has stable EMI shielding performances even after harsh conditions. • The film shows excellent comprehensive performance, including flexibility, thermal insulation and flame retardation. [ABSTRACT FROM AUTHOR]

With the continuous development of modern electronic technology, it is of great significance to explore materials with flexibility and stable electromagnetic interference shielding (EMI) properties in extreme environments. In response to this, a highly conductive polyimide-Ti 3 C 2 T x MXene-silver nanoparticles (PI-MXene-AgNPs) composite film was prepared by performing a self-reduction reaction on the surface of poly(amic acid) nanofibers. The polyimide nanofibers are wrapped with Ti 3 C 2 T x nanosheets and AgNPs. The film has excellent EMI shielding performance in X-band (8.2–12.4 GHz). When the mass ratio of MXene/AgNO 3 is 4:1, the PI-MXene-AgNPs films have high absolute EMI shielding effectiveness up to 16785.67 dB cm2 g−1 at a thickness of 30 μ m. The composite film has stable EMI shielding performance even after high (300 °C) temperature, cryogenic (−196 °C), corrosive environment, multiple bending and physical shaking. Furthermore, PI-MXene-AgNPs films exhibit excellent flexibility and superior mechanical properties that can be maintained even after treatment under harsh conditions. In addition, the PI-MXene-AgNPs composite films show good versatility, such as photothermal conversion properties, antibacterial properties. Therefore, this work provides a feasible strategy for the preparation of flexible electronic devices in extreme environments. [Display omitted] [ABSTRACT FROM AUTHOR]