Thermophysical Characterization of Lubricants Additivated with Nanoparticles for their Application in Renewable Energies

Abstract

This PhD Thesis is focused on the analysis of thermophysical and tribological properties of synthetic and mineral base oils, commercial lubricants (gearbox and motor oils) and new formulated nanolubricants. Nanoparticles of different morphology (spherical, rod-like and laminar) were used as lubricant additives: zirconium oxide and boron nitride nanoparticles together with graphene nanoplatelets. In order to propose new potential lubricants it is of vital importance to analyse the effect that the addition of the nanoadditives has on their thermophysical properties, because they affect the final lubricants performance. With this aim, the volumetric and viscous behaviour, viscosity index, flow curves and thermal conductivity were experimentally obtained. In order to know the mechanisms that control the tribological performance it is also necessary to determine the pressure-viscosity coefficient for elastohydrodynamic lubrication, the film thickness, the wear and the friction coefficient.