2D square nanosheets of Anatase TiO2: A surfactant free nanofiller for transformer oil nanofluids

Abstract

Rutile TiO2 nanoparticle with high dielectric constant has already become an automatic choice as a favorable nanofiller for efficacious transformer oil (TO) nanofluids (NFs) development, thanks to their large surface area and splendid electron trapping capacity. In this work, the role of phase and morphology of TiO2 on the properties of TO has been deciphered for the first time. For this, solvothermally prepared ultra-thin, square nanosheets of purely anatase phase TiO2 (a-TiO2) with 50–70 nm dimensions are used for NF preparation in two types of commercial mineral oil. The dielectric breakdown strength and thermo-physical properties of the resultant TO NFs have been investigated thereafter. A significant enhancement (27–30%) in breakdown voltage (BDV) at very low filler fraction (0.005 wt%) due to accelerated charge scavenging capability by virtue of the inherent surface oxygen vacancies, high electronegativity and slightly higher band-gap than rutile phase is observed. Additionally, the thermal conductivity of TO is seen to rise by 13–23% (±5%) at 50C which is facilitated by long phonon lifetime mediated inter-sheet transfer of heat. Further, the electronegativity induced strong repulsive forces among the dispersed nanofillers at ultra-low concentrations leads to a surfactant-free stable liquid insulation over a prolonged time. Besides, the acidity and viscosity, the increment of which with filler fraction causes a serious drawback for NFs, are below par the alarming level of TO due to low filler fraction of a-TiO2. All the above beneficial features along with improved flash and pour points makes the synthesized 2D a-TiO2 a budding candidate for efficient NF development at very low filler fraction without any usage of surfactant.