Constructing 3D hierarchical CNTs/VO2 composite microspheres with superior electromagnetic absorption performance

To achieve efficient electromagnetic wave absorption (EWA) performance with requirements of low density and thin thickness, three-dimensional (3D) hierarchical CNTs/VO2 composite microsphere was successfully synthesized though an ultrasonic atomization process in this work. The phase composition, morphology, EWA performance and corresponding mechanism were investigated. The VO2 microspheres (MS) was obtained via the complete reduction of V2O5 by oxalic acid, and the introduced CNTs were uniformly distributed around VO2 MS. The addition of CNTs both improved the impedance matching and provided multiple attenuation modes. The highly conductive CNTs enhanced conductivity further increasing conductance loss. Moreover, heterogeneous interfaces formed between CNTs and VO2 phase generated strong polarization loss. Furthermore, the construction of 3D structure not only benefited the stability of structure but also extended the paths of EW reflection and scattering thus consuming more EW energy. With the synergistic effect of favorable impedance matching and attenuation ability, the excellent EWA performance was achieved that the minimum reflection loss was −58.2 dB with the effective absorption bandwidth of 3.94 GHz in X band. This research plays a significant guiding role in structural construction and optimization of EW absorber.