A conductive mechanism of PVA (Mowiol 10-98) filled with ZnO and MWCNT nanoparticles

Abstract

Polyvinyl alcohol (PVA) hybrid nanocomposites are prepared via an ex situ approach with ZnO and MWCNT nanoparticle fillers and their conductive mechanisms have been investigated. The tailored hybrid nanocomposite conformation and their microstructural disparities for different filler concentrations were studied using an X-ray diffractometer. The direct current (DC) conductivity studies show an increase in the conductivity from $1.0528\times 10^{-11}$ to $2.1514\times 10^{-8}\hbox { S cm}^{-1}$ up to a percolation threshold filler concentration of $x=7.5$ wt%. The dielectric constant substantially indicates a decreasing trend with increasing frequency. The exaggerated dielectric constant values of 11.8 at 5 kHz, 6.3 at 100 kHz, 5.86 at 500 kHz and 2 at 1 MHz are observed for 7.5 wt% filler hybrid nanocomposites, which indicates their potential application as a gate material in metal-oxide-semiconductor field-effect transistors (MOSFETs). The alternating current (AC) electrical conductivity demonstrates an increasing behaviour up to $x=7.5$ wt% filler concentration. The smaller values observed in the real part of the electric modulus (${M}^{\prime })$ indicates a riddance in electrode polarization. The observed higher frequency shift in the imaginary part of the electric modulus for increasing the filler concentration up to $x=7.5$ wt%, decreases the relaxation time of the dipole orientation thereby increasing the conductivity mechanism of the hybrid nanocomposites. Apart from these, its small relaxation time with high electrical conductivity favours this material PVA/(x)MWCNT($15-x$)ZnO to have prospective application in microwave absorption appliances. The increase in the surface roughness of the film seen from the AFM images up to $x=7.5$ wt% concentration supports an enhancement in the crystalline nature of the filler. Differential scanning calorimeter studies show an enhancement in glass transition temperature ($T_{\mathrm{g}})$, melting temperature ($T_{\mathrm{m}})$ and decomposition temperature ($T_{\mathrm{d}})$ for PVA filled with MWCNTs and ZnO composites for optimum filler concentration $x=7.5$ wt%.