Enhanced electromagnetic interference shielding effectiveness of hybrid fillers by segregated structure

Polymer nanocomposites seem to be promising candidate for the electromagnetic interference (EMI) shielding material because of its loss cost, lightweight, flexibility, and ease of production. However, to achieve high shielding, there are concerns about the nanofiller concentration and dispersion of nanofillers in the polymer matrix. To overcome this issue, implementing the effective filler dispersion technique by segregated structure were investigated. In this study using miscible mixing and precipitation method (MSMP), polystyrene (PS) matrix was fabricated by incorporation of multiwall carbon nanotubes (CNT) as primary filler and nickel nanowires (NiNW) or zinc oxide nanowires (ZnONW) as secondary filler. Preparing a hybrid structure of the dielectric/magnetic nanofiller along with CNT led to significant increase in EMI shielding effectiveness (SE) when compared to the single filler systems. For instance, PS/2.0vol% CNT nanocomposites showed EMI SE of about 16.6dB (in X-band frequency) for 1.1 mm thick shield. By adding 0.5vol% of the secondary filler either NiNW or ZnONW, it enhanced the EMI SE to 23.2dB and 24.0dB respectively. This excellent EMI SE of the hybrid nanocomposites was attributed to both selectively distributed conductive nanofillers in a segregated structure and excellent magnetic/dielectric properties of the synthesized NiNW/ZnONW, respectively. Details of the dielectric loss mechanisms for the architectures were studied. Besides achieving reliable dielectric properties, CNT/NiNW or CNT/ZnONW nanocomposite shield can be prepared with low thickness and low filler content, making them useful for various shielding applications.