Morphology vs. Specific Surface Area: Which Plays the Leading Role in Microwave Absorption?

Abstract The hetero atoms existing in the backbone, specific surface area, pyrolysis temperature, and morphology of biomass pave the way for its microwave absorption. Herein, pilled jujube fruit is selected as the biomass source. The impact of the morphology on the microwave absorption is assessed by manipulating the drying procedures. Subsequently, carbon nanotubes (CNTs) are implanted using red phosphorus as both a catalyst and a doping agent. Following that, to further enhance the material's performance, the heterogeneous interfaces are broadened through in situ polymerization of indole. The final composite film is fabricated using polyacetylurea (PAU), synthesized from citric acid and urea. The role of the microwave absorbing medium is investigated by comparing results obtained from the polyethylene (PE) and PAU as absorbing matrices, illustrating the potential of the PAU in improving the shielding/absorbing capacities. In the interesting competition between the morphological features and specific surface area, the sample with a unique morphology and fewer heterogeneous interfaces demonstrated superior reflection loss (RL) with a thinner matching thickness as well as higher electromagnetic interference (EMI) shielding effectiveness (SE) and reduction of radar cross sections (RCS). The maximum reflection loss (RL max ) and SE is significantly boosted by implanting CNTs, and both properties are further promoted by incorporating the polyindole (PIN). According to our results, the specific surface area is necessary, but insufficient. In other words, the wrinkled morphology generated various polarized structures, establishing various meta/quasi‐antenna structures and leading to better microwave absorption. This phenomenon is observed for the sample dried at room temperature.