Rational design of hollow nanosphere γ-Fe2O3/MWCNTs composites with enhanced electromagnetic wave absorption

High-performance electromagnetic wave (EMW) absorbing materials have been widely used in the wireless communication and electronic devices due to their important potentials in electromagnetic attenuation. However, it is difficult to develop carbon-based absorbers with thin thickness, lightweight, and low filler loading. In this work, rationally designed hollow nanosphere gamma-Fe2O3/MWCNTs composites were successfully realized for ultrathin, lightweight, and high-efficiency EMW absorbers. It showed that the composition, microstructure, and morphology of composites were tailored, which gave rise to the tunable magnetic behavior, porosity, and electromagnetic parameters. The rational design of composition and novel structure contributed to the optimization of the impedance match. The EMW attenuation was enhanced by the synergistic effects of the dielectric loss originated from the interfacial and dipole polarization, conductive loss stemmed from the 3D conductive network, and the magnetic loss derived from the eddy-current loss and ferromagnetic resonance. Accordingly, the hollow nanosphere gamma-Fe2O3/MWCNTs composites with a low filling ratio of 20 wt% achieved an ultrathin matching thickness of 1.4 mm and a strong reflection loss of -63.6 dB. The substantially enhanced EMW absorbing performances were owing to the optimized impedance matching and enhanced attenuation capability. Therefore, this work can provide a paradigm for the design and synthesis of hollow nanosphere gamma-Fe2O3/MWCNTs composites with an enhanced EMW absorption. (C) 2019 Elsevier B.V. All rights reserved.