Construction of 3D Fibonacci Cauliflower-Like NiCo 2 S 4 /Expanded Graphite Heterogeneous Structures for Enhanced Electromagnetic Wave Absorption.

Highly efficient electromagnetic wave (EMW)-absorbing multicomposites can be fabricated by constructing particular structures using suitable components. Expanded graphite (EG) has a 3D, low-density porous structure; however, it suffers from poor impedance matching and EMW absorption properties. Based on this information, in the present study, NiCo 2 S 4 components with different morphologies are successfully loaded onto a 3D EG surface using a facile microwave solvothermal method to achieve a synergistic effect between the different components. The NiCo 2 S 4 content is adjusted to alter the compositional morphology and electromagnetic parameters of the composites to achieve impedance-matching and obtain excellent EMW absorption properties. The heterogeneous interface between EG and NiCo 2 S 4 induces an inhomogeneous spatial charge distribution and enhances interfacial polarization. The defects in the material and oxygen-containing groups induce dipole polarization, which enhances the polarization-relaxation process of the composites. The 3D porous heterostructure of the "Fibonacci cauliflower"-shaped NiCo 2 S 4 /EG composites results in an optimal reflection loss of -64.93 dB at a filler rate of only 14 wt.%. Analysis of the synergistic conduction loss and polarization loss mechanisms in carbon-based materials with heterogeneous interfaces has led to the development of excellent EMW absorption materials.