Enhanced microwave absorption of flower-like FeNi@C nanocomposites by dual dielectric relaxation and multiple magnetic resonance

Abstract

Flower-like FeNi@C nanocomposites self-assembled by FeNi nanosheets and flocculent carbon were synthesized by the hydrothermal method. The electromagnetic parameters of FeNi@C–paraffin composites were measured at 0.03–18 GHz. Dual dielectric relaxations were observed in the composite system due to the cooperative consequence of the FeNi–C interfaces and dielectric carbon. The strong magnetic loss is from the coexistence of natural resonance and exchange resonance. For the 2.0 mm thickness layer, an optimal reflection loss (RL) of −46.7 dB is observed at 3.17 GHz, whereas the absorbent with a thickness of 1.3 mm has an RL of −32.78 dB at 13.78 GHz. The excellent microwave absorption abilities result from the synergy of dielectric and magnetic losses and quarter-wavelength cancellation.