Non external field adsorption regulation mechanism of nanoparticles in lubricating fluid on metal and non-metal surfaces based on solvent-induced surface polarity change

In terms of the use of nanoparticles as lubricant additives, it is essential to achieve their rapid and high-quality adsorption onto the surfaces of different frictional pairs, to realize efficient lubrication of multiple friction pairs with one lubricant at the same time. In this study, solvent-induced method was used to reasonably regulate the diisooctyl dithiophosphate (DDP) modified Cu nanoparticles (denoted as CuDDP) in lubricating oil zeta potential. The adsorption behavior of nanoparticles in lubricating fluids under electrostatic force (FE) and driving force (FD) on the surfaces of metal and non-metallic diamond-like carbon (DLC) coatings without external field action was studied, as well as their tribological properties between metal–metal/non-metal. Research has found that the FE of CuDDP on the surfaces of two types of friction pairs varies with the zeta potential linear increase with increasing, while the combined effect of fluid flow rate and the size of agglomerated nanoparticles can lead to differences in the FD they are subjected to; and when the FE and FD are in equilibrium, the adsorption equilibrium is reached. The equilibrium adsorption mass and adsorption rate impact the tribological performance of nanoparticles. In short, solvent-induced treatment delivers superior adsorption and tribological properties of nanoparticles.