Synthesis and enhanced electromagnetic wave absorption performances of Fe3O4@C decorated walnut shell-derived porous carbon

Abstract

Bio-derived carbon is considered to be an ideal lightweight dielectric-type electromagnetic wave absorbing material (absorber). However, the vast majority of them cannot achieve satisfactory absorption performances just depending on dielectric loss. Herein, to obtain a superior electromagnetic wave absorber, Fe3O4@C nanospheres have been successfully decorated on the surface of the biomass (walnut shell)-derived porous carbon (BC) via a hydrothermal-calcination process. It is worth noting that the dielectric constant and permeability matching as well as corresponding electromagnetic wave absorption properties of the absorber can be effectively enhanced by adjusting the content of Fe3O4@C nanospheres. The as-synthesized optimal sample (BC/Fe3O4@C-2#) exhibits superior electromagnetic wave absorption performances with the minimum reflection loss (RL) value of −56.61 dB and wide effective absorbing bandwidth (EAB) of 2.72 GHz at 2.46 mm matching thickness, meanwhile, the widest EAB with the value of 5.68 GHz can be achieved at 1.46 mm thin matching thickness. Starting from the respective advantages of dielectric, magnetic and material components, a reasonable synergistic mechanism, including multiple reflection, Debye relaxation, interface polarization and other mechanisms are demonstrated to transmission and loss processes. This low cost, simple preparation process and excellent absorbing performance promise BC/Fe3O4@C nanocomposites being an excellent lightweight electromagnetic wave absorber.