Multifunctional SiO₂-wrapped CNFs@NiFe₂O₄ nanocomposites for excellent electromagnetic wave absorption, hydrophobicity, and thermal insulation performance

The electromagnetic wave (EMW) absorbing materials used in harsh working environments are susceptible to thermal degradation and dielectric constant drift caused by humidity fluctuation, which severely restricts their practical applicable in aerospace, marine engineering and advanced electronics. Herein, a hierarchical nanoarchitecture consisting of silica-coated carbon nanofibers uniformly anchored with NiFe₂O₄ nanosheets (denoted as CFNOS) is fabricated via a combined electrospinning-hydrothermal-carbonization route. This ternary structural design circumvents the inherent drawbacks of pristine carbon nanofibers through synergistic dielectric and magnetic loss: NiFe₂O₄ introduces dominant magnetic loss, while the outer silica shell strengthens interfacial polarization to realize efficient EMW dissipation. The optimized CFNOS-2 delivers a minimum reflection loss (RL_min) of -59.10 dB at 1.68 mm, together with an effective absorption bandwidth (EAB) of 5.04 GHz at 1.60 mm, exceeding most previously reported carbon-based absorbers. Benefiting from the protective silica layer, CFNOS-2 possesses robust environmental adaptability, featuring a water contact angle of 139.1°, residual mass exceeding 80% upon heating to 800°C, as well as favorable thermal insulation and infrared stealth performance (surface temperature maintained at 120°C over 45min). This work provides a facile structural strategy toward high-performance EMW absorbers applicable for extreme environments, paving a feasible route for next-generation stealth devices and high-density electronic packaging.