Investigation of size and morphology effects of MgO nanostructures on the properties of MgO/transformer oil-based nanofluids

MgO nanoparticles and nanoflakes were prepared using sol–gel and hydrothermal methods, and the effect of size and morphology of MgO nanostructures on the thermal conductivity and stability of the transformer oil-based nanofluid containing these nanostructures was investigated. The structural properties of the samples were examined using X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM). The results showed that the nanostructure’s shape depends on the fabrication method, pH, temperature, and synthesis time. Also, the measurements showed that the thermal conductivity of nanofluids containing MgO nanoflakes with different wt% has higher values than that of nanofluids containing MgO nanoparticles. It was found that by increasing the concentration of nano additives up to 1 wt%, the thermal conductivity increased and then decreased for higher concentrations. The maximum increase of 11.3% was measured for nanofluid containing 1 wt% of nanoflakes. Likewise, the stability of nanoflake’s nanofluid was observed to be higher.