Controlling the microstructure of biomass-derived porous carbon to assemble structural absorber for broadening bandwidth

Recently, biomass-derived porous carbon has received attention in many fields due to its low-cost and environmental friendliness. Attribute to the high dielectric loss of carbon materials, the microwave absorbers which is made of biomass-derived porous carbon can meet the low-cost, simple preparation and basic microwave absorption. However, the high permittivity of carbon material tends to limit its impedance matching over a wide frequency range. Here, we prepared several porous carbon materials with different microstructure by a simple chemical activation process. Then, a double-layer structural absorber (SA) was designed based on these porous carbon materials. Specifically, the porous carbon composing the first and second layer of SA has great impedance matching, and strong dielectric loss, respectively. Therefore, the effective absorption bandwidth (EAB, reflection loss below −10 dB) of SA can reach 13.8 GHz (from 4.2 GHz to 18 GHz). This work provides a new prospect for the recycling and reusing of waste biomass materials and a facile low-cost route to design the broadband structural microwave absorbers.