Transform between the permeability and permittivity in Ni@CCNbC nanocomposites with enhanced microwave absorption properties

•Ni@CCNbC nanocomposites are prepared by arc discharge method.•Ni@CCNbC nanocomposites exhibit large permittivity and enhanced dielectric loss.•An anomalously electromagnetic resonance appears at ∼12 GHz.•An unusual energy transfers from the permeability to permittivity at ∼12 GHz.•The RL value reaches −40.4 dB at 8.48 GHz with the absorbent thickness of 3.2 mm.

We report the microwave absorption properties of a composite system comprising of core-shell structured Ni@C nanocapsules, defective onion-like carbon nanoparticles and NbC nanoparticles. Compared with Ni@C nanocapsules, the Ni@CCNbC nanocomposites exhibit large permittivity, enhanced dielectric loss and three Debye dipolar relaxations. An anomalous electromagnetic resonance in the Ni@CCNbC/paraffin system appears at ∼12 GHz, revealing an energy transform from the permeability to permittivity. The reflection loss value of the Ni@CCNbC/paraffin composites reaches −40.4 dB at 8.48 GHz with the absorbent thickness of 3.2 mm. Experimental results coupled with theoretical calculations by the Cole-Cole equation and the delta function standing for the electromagnetic matching degree further reveal that the good microwave absorption originates from the enhanced dielectric loss and improved electromagnetic matching.