On the Dielectrical, Electrical and Thermo-Physical Properties of Magnetite Nanoparticle-Doped Synthetic Ester

This study reports on engineering of stable magnetite nanofluids for application in high voltage technology. Iron oxide (Fe ₃O ₄) nanoparticles were synthesized by the bottom-up approach. Nanofillers were functionalized with a surfactant and subsequently dispersed in a diluent. Nanoparticles were characterized with transmission electron microscopy (TEM), thereby the average size of 10 nm was determined for nanoparticles in concentrated solution. This colloid is diluted in synthetic ester as base liquid in two concentrations. The high stability of the colloids was confirmed with dynamic light scattering (DLS). AC breakdown voltage beside dielectric properties of the nanofluids were measured. The results show a significant improvement of the breakdown voltage strength. Magnetite nanoparticles are de facto electrically conductive, therefore addition of magnetite nanofillers gives rise to dielectric loss factor. However, magnetite nanoparticles possess much higher relative permittivity compared to the used working fluid, relative permittivity of the colloid increases slightly by infusion of the nanofillers. The thermal conductivity and dynamic viscosity were measured using a transient hot wire setup and a rotational rheometer, respectively. A moderate enhancement in thermal conductivity of the magnetite nanoparticledoped fluid was observed; being intensified with temperature increase. The dynamic viscosity of the prepared fluids remains unchanged despite infusion of the nanoparticles. However, the results turn out significant enhancement in electrical properties and moderate improvement in thermos-physical properties of the nanofluids; holistic investigations should be conducted to achieve an optimized formulation in terms of the type and concentration of the nanoparticle.