Significantly elevated AC dielectric strength of synthetic ester oil-based nanofluids by varying morphology of CdS nano-additives

Abstract

Synthetic ester (SE) oil-based nanofluids (NFs) are indispensable for high voltage (HV) applications due to their impressive properties; for instance, high biodegradability, environmental friendliness, high dielectric strength and thermal stability. In this work, the solvothermal route is adopted to synthesise cadmium sulfide (CdS) nanomaterials of three different morphologies. CdS nanoparticles (NPs) possess a zinc blende (cubic) phase; however, CdS nanobelts (NBs) and CdS ultra-thin nanosheets (NSs) exhibit a wurtzite (hexagonal) phase. Thereafter, CdS nano-additives are dispersed in SE oil (MIDEL-7131) to investigate the influence of phase, morphology and bandgap of nano-additives on the AC breakdown characteristics of nanofluids. The resultant NFs exhibit significantly augmented AC breakdown strength because of expedited charge scavenging ability due to high bandgap and the formation of an electrical double layer (EDL). NPs based nanofluid (SE/NPs), NBs based nanofluid (SE/NBs), and NSs based nanofluid (SE/NSs) display their optimum doping concentration of 0.3 g/L, 0.3 g/L, and 0.2 g/L, respectively. Furthermore, the thermal stability of NFs of optimum doping concentration is investigated and compared with SE via TGA/DSC/DTG technique. The findings evince that the initial decomposition temperature is high and heat dissipation is low in NFs compared to SE, which indicates that the nanofluids are thermally stable both in air and nitrogen. Finally, the kinematic viscosity measurements of NFs of optimum doping concentration exhibit slightly lower viscosity than that of SE. Hence, CdS nano-additive is proved to be a magnificent potential aspirant which is highly efficient for insulating oil-based NFs development without any surfactant.