Multiple interface coupling in halloysite/reduced graphene oxide/ cobalt nickel composites for high-performance electromagnetic wave absorption.

Here in this article, a halloysite nanotube/reduced graphene oxide/cobalt nickel composite (HNT/rGO/CoNi) was synthesized by co-precipitation and subsequent calcination processes. The microstructure, morphology, and chemical composition of the as-synthesized samples were characterized by X-ray diffractometer, Raman spectra, scanning electron microscopy, transmission electron microscopy, and X-ray photoelectron spectroscopy. The electromagnetic absorption performances of the composites/paraffin wax hybrids were tested in the frequency range 2-18 GHz. It was found that the synergistic attenuation of electricity and magnetism, as well as the fairly good impedance matching properties together have led to the impressive electromagnetic absorption performance of the optimized product. The maximum reflection loss can reach - 69.77 dB with the thickness of 2.38 mm at 14.72 GHz, and an effective absorption bandwidth of about 7.12 GHz (10.88 GHz-18.00 GHz) can be achieved in the HNT/rGO/CoNi (30) composite. The excellent microwave absorption performance was estimated to originate from the combination of multiple electromagnetic loss mechanisms, including interfacial polarization between graphene and magnetic nanoparticles, dipole orientation polarization caused by the defects of graphene, the natural ferromagnetic resonance, and eddy current of the magnetic nanoparticles. Furthermore, the halloysite plays the roles of improving dispersion of the magnetic nanoparticles as well as adjusting the complex permittivity of the composite. This work provides a new strategy for the design and fabrication of high performance microwave absorbing materials with natural and readily available components.