Morphology-driven multifunctionality: tailoring ZnO for enhanced EMI shielding and energy harvesting in PVDF/MWCNT nanocomposites
Aleena Sabu, U Pooja, Meera B. Nair, Dinesh K. Shukla, Rajkumar Patel, Pratheep K. Annamalai, Amit Malakar, Suryasarathi Bose, Ramanujam Brahmadesam Thoopul Srinivasa Raghava
Abstract
This research establishes a critical correlation between the morphologies of zinc oxide (ZnO) inclusions and the emergent electrical, electromagnetic interference (EMI) shielding, and energy harvesting (piezoelectric and triboelectric) properties of poly(vinylidene fluoride) (PVDF)-multiwalled carbon nanotube (MWCNT) hybrid nanocomposites. Strikingly, incorporation of a low concentration (0.05 wt%) of ZnO nanospheres, with polyvinylpyrrolidone (PVP), led to a two-order-of-magnitude enhancement in the electrical conductivity of the PVDF-7 wt% MWCNT matrix, surpassing the binary composite and a four-order-of-magnitude increase over the ZnO rod-modified counterpart. This morphological advantage was translated into superior EMI shielding, with the ZnO nanosphere-incorporated hybrid nanocomposite (0.2 mm thickness) exhibiting a total shielding effectiveness of 24.72 dB, nearly double that of the rod-modified system (12.91 dB) at 10 GHz. Conversely, the hybrid nanocomposite with ZnO rods resulted in a higher piezoelectric output voltage of 3.95 V under mechanical stimulus, while ZnO nanosphere inclusion resulted in a higher triboelectric output voltage of 6.72 V. These divergent behaviours are mechanistically linked to the electroactive γ-phase content of PVDF, confirmed through X-ray diffraction, Fourier transform infrared spectroscopy, and differential scanning calorimetry, and the surface roughness of the composite, respectively. The distinct dispersion characteristics of the ZnO fillers within the PVDF-MWCNT matrix were elucidated through dynamic mechanical analysis.