Recently, improving the applicability of transition-metal carbon/nitride (MXene) shielding devices through integration with nanomaterials and polymers has gradually attracted the attention of researchers. Although the addition of an insulation enhancement phase improves the mechanical properties of MXene shielding devices, it is still a challenge to avoid extensive damage to the conductive network and the reduction of the shielding efficiency (SE). Herein, an effective approach is demonstrated to construct an ultralight, conductive Ti₃C₂T_x MXene/aramid nanofiber (ANF) anisotropic aerogel. Thanks to the strong interfacial interaction between the MXene nanosheets and ANFs, abundant rigid skeleton and “cell wall” structures were constructed in the anisotropic aerogel. The aerogel was not only endowed with excellent compressibility and superelasticity, but also built a macroscopic conductive network, thus increasing the impedance mismatch interface, and ensuring the electromagnetic interference (EMI) shielding performance of the device. At an ultra-low Ti₃C₂T_x content (0.58 vol%), the conductivity of the composite aerogel reached a maximum of 854.9 S m⁻¹ and the EMI SE reached 65.5 dB, which is the best efficiency value of an aerogel based on ANFs so far. In addition, the anisotropic Ti₃C₂T_x/ANF aerogel had consistent thermal stability and flame retardant properties. The nanosheet edge protection based on ANFs delayed the oxidation of MXene, and the EMI SE still reached 59.1 dB after 2 h of exposure in air at 250 °C. Therefore, the ultralight, superelastic, and thermally stable Ti₃C₂T_x/ANF anisotropic aerogel prepared in this work showed excellent application prospects in various extreme conditions.

This study proposes a novel and facile method to synthesize high-quality NH₂-functionalized and carboxyl-functionalized graphene oxide (PPD–CFGO)/polyimide (PI) composite films with high dielectric constant (ε), low dielectric loss, high-temperature resistance and outstanding mechanical properties by in situ polymerization. In addition to the partial carboxyl groups located at the edges, the ample hydroxyl and epoxy groups bonded on the basal plane of graphene sheets were exploited to covalently bond to the amines. GO was modified by oxalic acid to obtain carboxyl-functionalized GO (CFGO) before amidation. NH₂-functionalized CFGO (PPD–CFGO), dispersing well in dimethylacetamide (DMAc), was the initial platform for polymer grafting to improve the CFGO dispersion in the polymer matrix. Partially reduced graphene nanosheets are formed during the imidization process. The PPD–CFGO/PI composite films exhibit high tensile strength (up to 848 MPa) and Young's modulus (18.5 GPa). The thermogravimetric analysis results indicate that the PPD–CFGO/PI composites have good thermal stability below 500 °C. The dielectric constant increases up to 36.9 with an increasing amount of PPD–CFGO, higher than that of the pure PI polymer by a factor of 12.5, while the dielectric loss is only 0.0075 and the breakdown strength still remains at a high level (132.5 ± 9.3 MV m⁻¹).

Three-phase composite films CCTO@MWCNT/PDMS with enhanced dielectric constant (ε) and low dielectric loss are prepared by embedding covalently bonded calcium copper titanate (CaCu₃Ti₄O₁₂, CCTO) with multi-walled carbon nanotubes (MWCNTs) composite nanoparticles (CCTO@MWCNT), forming a chain-ball structure, into the polydimethylsiloxane (PDMS) matrix. To impede the natural stacking of MWCNTs, CCTO particles are functionalized first with a silane coupling agent containing amino groups, and then react with carboxyl-functionalized MWCNTs (MWCNT-COOH) to achieve the strong linkage between CCTO and MWCNTs, confirmed by the FTIR spectrum and SEM images, etc. The chain-ball CCTO@MWCNT nanoparticles have effectively improved the dielectric permittivity of PDMS. The dielectric constant of the CCTO@MWCNT/PDMS composite film, agreeing well with the percolation theory, is up to 2133 at 1 kHz, higher than that of pure PDMS by a factor of 700, when the volume fraction of MWCNTs approaches the percolative threshold. Meanwhile, the dielectric loss is only 0.19. For comparison, CCTO/PDMS and MWCNT/PDMS films are prepared and investigated as well. The Yamada model can effectively predict the dielectric constant of CCTO/PDMS composite films. The dielectric constants of CCTO/PDMS and MWCNT/PDMS films are 1/180 and 1/6, respectively, in comparison with that of CCTO@MWCNT/PDMS. The tensile strength of CCTO@MWCNT/PDMS approaches 1.12 MPa, 3 times higher than that of pure PDMS.