Hollow FeNi/NiFe₂O₄-Codoped Carbon Composite Nanorods for Electromagnetic Wave Absorption

Electromagnetic wave absorbers (EMWAs) with light weight, strong absorption, broad absorption width, and thin thickness are in high demand. Metal–organic frameworks are considered to be an emerging type of ideal sacrificial precursor to synthesize multicomponent magnetic nanoparticles/porous carbon composites. Most of these multicomponent composites exhibit brilliant electromagnetic-wave-absorbing performances because of multifarious absorption mechanisms and better impedance matching. In this work, hollow spindle-shaped FeNi/NiFe2O4-doped carbon composite nanorods, denoted as FeNiC, were synthesized by one-step calcination of FeNi bimetallic MIL-101 at 600, 700, and 800 °C. A strong reflection loss (RL) of −62.7 dB and a broad effective absorption bandwidth (Δfe) of 7.46 GHz (12.4–18 GHz) covering the entire Ku band were optimized through control of the calcination temperature and thickness of paraffin wax. The remarkable EMWA performance was mainly attributed to the synergistic effect of hierarchical pores, geometric structure, and dielectric and magnetic losses. This work may provide an inspiring method to integrate multiple components and hierarchically porous structures to achieve lightweight and broadband EMWAs.