Investigation on ethylene glycol and glycerol mixture concentration dependent optical, dielectric, electrical, rheological, and thermophysical properties of EG+Gly/ZnO semiconductor nanofluids

Abstract

Wide energy bandgap metal oxide nanomaterials containing semiconductor nanofluids (SNFs) are technologically established as advanced multifunctional materials for progress in high performance soft condensed devices. Therefore, to strengthen this field of materials, the present study reports in detail the optical, dielectric, electrical, rheological, and thermophysical properties of the SNFs based on ethylene glycol (EG) and glycerol (Gly) mixture of an entire concentration range (Gly volume fractions; 0.00, 0.25, 0.50, 0.75, and 1.00) with a fixed amount of zinc oxide (ZnO) semiconductor nanomaterial (0.05 wt%). These green-formulated EG + Gly/ZnO SNF materials showed a longer stability of the suspended nanoparticles in the highly viscous hydrogen bonded base fluid and exhibited an increase in absorbance with the decrease wavelength of visible range photons and the ZnO electronic transition at about 3.2 eV energy of ultraviolet radiations. Dielectric measurements over the 20 Hz–1 MHz range of these SNFs, at 298.15 K, explained a dominant contribution of the electrode and interfacial polarization processes at low frequencies and the molecular dipole polarization of static permittivity about 40 at the higher frequencies. Electrode polarization and conductivity relaxation times enhanced exponentially when the Gly concentration increased in the EG + Gly base fluid which governs the electrical conductivity decrement from 0.79 to 0.04 μS/cm for these SNFs. The rheological study explained the Newtonian characteristics of EG + Gly/ZnO nanofluids with their base fluid mixture concentration controllable dynamic viscosity in the wide range of 17–702 mPa s, at 298.15 K. The density, refractive index, ultrasound velocity, prominent acoustic parameters, and thermal conductivity are determined and discussed to explore the solid-liquid interaction and interfaces formed in these innovative SNF materials.