Morphology and medium influence on microwave characteristics of nanostructures: A review

Nowadays, electromagnetic pollution originated from artificial intelligence devices, fifth-generation (5G) cellular networks, as well as ever-increasing electronic devices applying and/or producing electromagnetic waves has excited the global concern. Evidently, the novel threats are springing up as a sleeping giant awaiting to irrupt; thus, the immediate counteraction is inescapable against the augmenting harmful electromagnetic waves. Till date, based on the permeability and permittivity of the materials in the microwave region, diverse microwave absorbing structures have been fabricated to overcome the aforementioned problem. It is worth noting that nanostructures are under the spotlight as a hot spot generated from their incomparable surface area-to-volume ratio tuning polarizability, magnetic features, electrical conductivity, eddy current loss, and other absorbing mechanisms. It should be noted that the secondary pollution produced at the threshold of the absorbing structures is tunable by the impedance matching. Hitherto, the size, shape, and morphology of nanostructures have been manipulated to improve microwave attenuation. The more surface area-to-volume ratio brings the more defect, dipole, and interfacial polarization as well as enhances the interfacial interactions at heterogeneous interfaces providing more multiple reflections and scattering. On the other hand, the intrinsic properties of the absorbing media and their unique interactions at grain boundaries can promote microwave attenuation which have recently attracted a great deal of attention. The obtained results manifest that the morphology and medium influence on microwave absorbing characteristics are the tip of the iceberg investigated by diverse approaches. In this study, a comprehensive prospect is presented using recent researches related to the size, shape, defect, morphology, and medium effect on the microwave absorbing mechanisms paving the way for microwave attenuation. The achieved works have attested that the mentioned parameters are the vital factors influencing the microwave absorbing properties.