Dependency of tunable electromagnetic wave absorption performance on morphology-controlled 3D porous carbon fabricated by biomass

Abstract Using biomass as raw materials to fabricate porous carbon (PC) absorbing materials has become a hotspot. However, the effective medium to regulate the porous structure is often limited to control the heat treatment conditions including heating temperature, insulation time and heating rate. In this work, the pinecone was decided as raw materials and four different activators (KOH, NaOH, K2CO3 and ZnCl2) were chosen to investigate the effect of the type of activator on the porous structure. Meanwhile, the activation mechanisms were revealed as well. SEM results illustrate that the variety of activators has a remarkable influence on the pore size of porous. Based on Maxwell-Garnet theory, the size of the aperture will affect the impedance matching of absorber. According to the electromagnetic (EM) parameters, the porous carbon activated by KOH (KOH-PC), NaOH (NaOH-PC) and K2CO3 (K2CO3-PC) exhibited excellent impedance matching compared to other absorbers. Thus, the KOH-PC, NaOH-PC and K2CO3-PC exhibit sterling EM wave absorption performance. Particularly, the minimum reflection loss of K2CO3-PC could be up to −76.0 dB at the matching thickness of 2.1 mm and the broadest effective absorption bandwidth was 5.92 GHz covering from 11.92 to 17.84 GHz at 2.3 mm. The excellent EM wave absorption performance could ascribe to the synergistic effect of conductive loss, space charge polarization and dipolar loss. Besides, the influence of the addition amount of activators to the porous structure was also investigated. This work offers a reference for the structural control of biomass porous carbon absorber.