Porous hybrid scaffold strategy for the realization of lightweight, highly efficient microwave absorbing materials

Exploring an advanced and efficient electromagnetic (EM) wave absorbing material by improving dielectric loss capacity and adjusting impendence matching is crucial yet challenging. Herein, the bacterial cellulose (BC) derived carbon aerogel (CA) with a robust nanofibrous network was used as a conductive loss scaffold to dissipate EM waves effectively, and the ZnO microparticles with excellent dielectric properties and low electrical conductivity were decorated on the scaffold to adjust dielectric parameters and impedance matching adequately. By using different zinc precursors, the tunable size and morphologies of ZnO crystals were obtained due to the growth rate of different crystallographic, including flower-like, nanorod like, and cauliflower-like morphologies, which is beneficial to strong multiple reflections, intensive interfacial polarization, better impendence matching, as well as excellent maintenance of the hierarchical structure. Owing to the appropriate impendence matching and the considerable EM wave dissipation, the CA@ZnO composites achieve a superior EM absorbing performance with a broad effective absorbing bandwidth (whole X band) and a minimum reflection coefficient (−53.3 dB). This work paves a new way for developing lightweight and highly efficient EM absorbing materials comprising the carbon scaffold and semiconductor microparticles.