Construction of chiral-magnetic-dielectric trinity composites for efficient microwave absorption with low filling ratio and thin thickness

The combination of carbon nanomaterials and magnetic nanomaterials has been proven to be a promising strategy to fabricate thin and lightweight microwave absorbers with tunable absorption bands and broadened bandwidth, especially the absorption capability in low frequency (2–10 GHz). Herein, a series of CoNi-based magnetic nanomaterials have been synthesized on the surfaces of chiral carbon nanocoils (CNCs) to form a chiral-magnetic-dielectric trinity composite through solvothermal reaction followed by a subsequent annealing method. The well-dispersed CoNi nanostructures enhance the magnetic loss of the composites, giving rise to the strong microwave absorption at low frequency. In addition, the dielectric CNCs with excellent chirality and dispersibility not only provide conduction loss and cross-polarization loss to broaden the absorption bandwidth, but also reduce the filling ratio of the composites. Accordingly, with the synergistic effect of the chiral-magnetic-dielectric components, combined with the good impedance and quarter-wavelength matchings, the trinity composite exhibits superior microwave absorption performance with a wide effective bandwidth of 6.1 GHz at the thickness of 1.85 mm. More importantly, the reflection loss value reaches −42 dB at 4.5 GHz with a low filling ratio of 12 wt%. This study provides a novel chiral-magnetic-dielectric trinity structure for highly efficient microwave absorption.