Investigation of sustainable porous carbon as radar absorbing material

Radar Absorbing Materials (RAMs) are composite materials able to attenuate an incident electromagnetic wave. Usually, RAMs are made of a polymeric matrix and an electromagnetic absorbent filler, such as silicon carbide or carbon black. Several materials have been investigated as potential fillers, aiming to improve the Reflection Loss (RL) and absorption bandwidth broadening. In this paper, a composite made with silicone rubber and biochar was investigated as a sustainable porous carbon made with biomass waste. Five different composites were characterized, composed of 1 - 5 wt.% of biochar in the silicone rubber. Although the RL of pure biochar composites is not significant, it was demonstrated here how a biochar composite can improve the RL of a RAM material when it is applied as a double-layer structure. While the RL of a ferrite-based RAM with 2.0 mm thickness reaches -28 dB, a combination of this RAM with biochar composite reaches ~ -60 dB with the same thickness. The double-layer structure with 2.3 mm thickness can have an absorption bandwidth of 2.95 GHz over the X-band frequency range, and a structure with 2.6 mm thickness can reach a RL of ~-76 dB. This demonstrates a sustainable, cheaper, and lighter material application (i.e., biochar), which is successfully used in the development of high-efficient electromagnetic shield or sensors. Keywords: Biochar, permittivity, RAM, sustainability, reflectivity.