Nanofilms of Fe₃Co₇ on a Mixed Cellulose Membrane for Flexible and Wideband Electromagnetic Absorption

Rapid development of wearable electronics stimulates the emergence of flexible electromagnetic (EM) wave absorbing materials with strong attenuation and wide bandwidth during deformation. Conventional EM wave absorbing materials are usually in the form of powders which are challenging to achieve satisfactory adhesion and/or dispersion in soft matrices. Here, uniform Fe3Co7 nanoparticles with large permeability have been electroless plated on a mixed cellulose membrane (MCM). The cross-linked cellulose endows the absorber with excellent flexibility and provides substantial heterogeneous nucleation sites for the Fe3Co7 nanoparticles in the formation of interconnected EM nanofilms, which give rise to enhanced polarization relaxation, conductive loss, eddy current effect, and ferromagnetic resonance. Optimal EM absorption with minimum reflection loss (RLmin) of −35.9 dB and ultrawide effective absorption bandwidth of 9.8 GHz has been achieved at a small thickness of 2.0 mm. Benefiting from the well-dispersed nanoparticles and stable adhesion onto the flexible substrate, the deformative Fe3Co7@MCM maintains effective absorption capacity during bending and compressing. This work not only clarifies synergistic attenuation mechanisms of flexible Fe3Co7@MCM in the natural and deformative states but also provides versatile strategy to construct flexible EM devices for extendable applications in catalysis, energy, and sensing.