Enhanced electromagnetic wave absorption property of hollow nanocubic trimetallic FeCoNi/C composites

Magneto-carbon composites are promising materials for mitigating electromagnetic pollution due to combined dielectric and magnetic loss mechanisms. However, such absorbers often have unsatisfactory wave-absorbing properties due to the difficulty in matching the magnetic permeability with the dielectric properties. The multilayered hollow carbon cubes anchored to a ternary FeCoNi alloy were fabricated using a self-tempered engineering strategy. The multilayer structures are formed in two steps and have an iron cobalt-nickel alloy core encapsulated in a hollow cubic carbon shell. Initially, a phenolic resin (PR)-coated FeCoNi-Prussian blue analogue (PBA) was prepared, followed by high-temperature vacuum pyrolysis. The inner carbon layer, derived from PBA, exhibits high crystallinity, while the outer PR-derived carbon layer is amorphous, preventing agglomeration of the carbonized FeCoNi alloy particles. The amorphous outer layer enables electromagnetic waves to be better absorbed and consumed within the absorber due to its ability to effectively modulate conductivity and impedance matching. By leveraging heterogeneous interface polarization and modulating electrical conductivity through control of graphite crystallinity, a minimum reflection loss (RL min ) of −74.2 dB and an effective absorption bandwidth (EAB) of 5.8 GHz across the 2–18 GHz range were achieved. The study provides an effective approach to broaden the application prospects of advanced magneto-carbon composite absorbers by using a multilayer structure to achieve a balance between magnetic loss and dielectric properties.