Effect of morphology and role of conductivity of embedded metallic nanoparticles on electromagnetic interference shielding of PVDF-carbonaceous-nanofiller composites

In this work, EMI shielding behaviors in the X-band frequency have been investigated for flexible polyvinylidene fluoride (PVDF) composites containing globular- and tubular-shaped carbonaceous nanostructures embedded with mono-metallic (Ni) and bi-metallic (FeNi, CoNi, MnNi) alloy nanoparticles. Pyrolysis was carried out at two different temperatures (800 degrees C and 1000 degrees C) to synthesize carbonaceous materials with two different morphologies. Carbon nanotubes (CNTs) are predominantly seen in the samples synthesized at lower temperature (800 degrees C), whereas carbon globules (CGs) are observed for the samples synthesized at higher temperature (1000 degrees C). The PVDF-CNT composites show superior microwave shielding behavior than the PVDF-CG composites, which is attributed to the enhanced absorption of the microwave through Ohmic conduction and interfacial polarization loss. The 1-D structure of CNTs provides the required conduction path for the electrons and forms a network to trap the microwave within them via multiple scattering. The microwave absorption behavior of the composites predominantly results from the metallic nature of the embedded nanoparticles, the graphitic layer encapsulating them and the graphitic walls of the CNTs. We further demonstrate the direct correlation of the EMI shielding behavior of the nanocomposites with the morphology of carbonaceous nanomaterials and the conductivity of the embedded metallic nanoparticles. (C) 2020 Elsevier Ltd. All rights reserved.