Ethylene glycol based silicon nitride nanofluids: An experimental study on their thermophysical, electrical and optical properties

Highlights: • Ethylene glycol based nanofluids containing various mass fractions Si₃N₄ nanoparticles has been prepared. • Flow and viscosity curves were presented with Herschel-Bulkley model fitting. • Thermal conductivity of Si₃N₄–EG nanofluids has been investigated. • Electrical conductivity of Si₃N₄–EG nanofluids has been presented as one of the biggest ever reported for nanofluids. • Optical properties: refractive index, transmittance and absorbance has been studied. This paper presents the results of an experimental investigation into the basic physical properties of silicon nitride (Si₃N₄) – ethylene glycol (EG) nanofluids. Samples with various volume fractions of nanoparticles were prepared using a two step method. Basic physical properties such as viscosity, thermal conductivity, electrical conductivity and optical properties were examined. A rheological investigation showed that silicon nitride ethylene glycol nanofluids present non-Newtonian shear thinning behavior. Thermal conductivity indicates a linear dependence on the volume fraction. As well as thermal conductivity increasing with increasing volume fraction, electrical conductivity is also related with the volume fraction of nanoparticles, and this relation is both very strong and nonlinear. The refractive index increases linearly with the volume fraction of nanoparticles in these nanofluids. Finally, it has been found that absorption of examined nanofluids is improved as the volume fraction of nanoparticles increases, especially in the UV region.