Studies on anomalous dispersion behavior of PANI–CNT composites for enhanced shielding effectiveness in various microwave bands

In this paper, the anomalous dispersion behavior of polyaniline–carbon nanotube (PANI–CNT) composites for various microwave bands is presented. The anomalous dispersion behavior is experimentally verified by observing group delay characteristics using vector network analyzer. In an anomalous dispersive medium, the transmission coefficient is characterized by an advancement in phase, while for a normal medium, the transmission phase shows a gradual decrease. By closely observing this property, we can correlate different material property deviations associated with the anomalous dispersion region of the sample in various microwave bands. The samples of PANI–CNT, in their powder forms, are used for the study. PANI–CNT is normally exhibiting diverse material properties compared with the normal EMI shielding materials which are inevitable for shielding applications. In this paper, the effect of anomalous behavior on various material parameters like permittivity and shielding efficiency (SE) is studied. The advantage of anomalous dispersion is that the region is characterized by a significant enhancement of SE as compared to the existing EMI shielding materials used for microwave applications.