High-efficiency microwave absorption performance of cobalt ferrite microspheres/multi-walled carbon nanotube composites

Abstract

In this article, spinel ferrite CoFe₂O₄ and multi-walled carbon nanotubes (MWCNTs) composites are constructed by a facile one-step solvothermal method. The pure phase of CoFe₂O₄ particles is confirmed by X-ray diffraction patterns. Microstructure analysis demonstrates that monodisperse CoFe₂O₄ microspheres are wound by MWCNTs. With the introduction of CNTs, there is a significant enhancement in the imaginary part of permittivity (ε″) with the composites. The champion microwave absorption performance can be achieved in the composites by the balance of complex permittivity and permeability. When the mass fraction of CNTs is 3%, a minimum reflection loss (RL_min) of the composites is as high as − 46.65 dB at 14.4 GHz at a thin thickness of 1.5 mm, and the corresponding effective absorption bandwidth below − 10 dB reaches 4.91 GHz ranging from 12.41 to 17.32 GHz which covers almost the whole Ku band (12.0–18.0 GHz). In other words, these as-synthesized composites show the most outstanding specific RL_min of − 31.1 dB mm⁻¹. Such superior microwave absorption behaviors of CoFe₂O₄/CNTs originate mainly from multiple dielectric relaxation processes, enhanced impedance matching and magnetic loss, as well as the considerable interface between mesoporous CoFe₂O₄ hollow microspheres and CNTs, thereby promoting microwave reflection and scattering within the samples. Our results indicate that as-fabricated CoFe₂O₄/CNTs composites can be a promising microwave absorbent integrating with a thin thickness, strong absorption ability, and broad bandwidth absorption.