Preparation, characterization and cooling performance of ZnO based Nanofluids

Nanoparticles (NPs) of Zinc Oxide (ZnO) were synthesized by the sol–gel method. These NPs were characterized for structural vibrational, morphological, optical, and electrical properties by X-ray diffraction (XRD), Fourier Transform infrared (FT-IR) spectroscopy, Scanning Electron Microscopy (SEM), UV–Visible optical absorption spectroscopy, and dielectric spectroscopy. Structural analysis confirms that all the NPs have a single-phase rutile tetragonal structure. Also from the Scherer formula, the average particle size for this compound was found to be around 10.25 nm. From SEM images, the observed NPs are spherical in shape, with an average size ranging from 10 to 100 nm. FT-IR data indicates a Zn–O vibrational bond and confirms the ZnO structure. Further, according to the optical data analysis, these NPs show an optical band gap of around 3.27 eV and follow an indirect transition. The dielectric constant (ε r ) and loss constant (ε) show good dispersion with the applied frequency. Also using these NPs, a nanofluid in transformer oil (mineral oil) was prepared. Further ε r & ε i shows good variation with the contents of NPs in the mineral oil. This nanofluid was tested for the cooling of transformers and shows some encouraging results. Based on these results, this material seems like a good candidate for transformer insulation and cooling applications.