In situ constructed honeycomb-like NiFe₂O₄@Ni@C composites as efficient electromagnetic wave absorber

Rational excogitation of microstructure and chemical constituents is a superior means of constructing electromagnetic wave (EMW) absorption materials with high performance. In this study, a kind of honeycomb-like NiFe₂O₄@Ni@C composite is prepared via an uncomplicated polymerization, pyrolysis and etching. Porous structure and internal cavity of NiFe₂O₄@Ni@C contribute to the numerous reflection and scattering of EMW. The strong ferromagnetic resonance of NiFe₂O₄ core and the multiple relaxation processes of porous carbon shell strongly promote the EMW loss. Additionally, the synergistic effect can improve impedance matching. The results demonstrate that the minimum reflection loss (RL) of honeycomb-like NiFe₂O₄@Ni@C composites is -65.33 dB at 13.63 GHz. The effective absorption bandwidth (EAB) is 3.68 GHz when the matching thickness is 4.95 mm. The mechanism of EMW dissipation of the honeycomb-like NiFe₂O₄@Ni@C composites is attributed to multiple reflections and scattering, conductive loss, interfacial polarization and ferromagnetism resonance. This work provides a tactic for the excogitation and synthesis of a low cost, light weight and efficient EMW absorber.