(222aa) Nanotribological Responses of Nanoparticle Solutions

Molecular dynamics modeling and simulation studies have been perform to investigate the nanotribilogical responses of nanoconfined nanoparticle solutions under time-continuous shearing.  The results show that when nanoparticles are added as nanolubricant additive, the tribological responses of the resultant nanoparticle solution thin films depend on a number of factors, including surface separation (film thickness), shear rate (sliding speed), nanoparticle size, nanoparticle volume fraction, and surface microstructure, and exhibit complex interplay among these factors.  At sufficiently large surface separations, nanoparticles tend to be well solvated but unable to break through the dense adjacent layers of solvent molecules to establish direct contact with the surfaces, thereby having only minimal effects on the apparent viscosity.  However, when the surface separation becomes comparable to the size of nanoparticles, nanoparticles can significantly alter the layered configurations and in-plane ordering of the solvent molecules.  It was found that the magnitude and trend of the apparent viscosity of a thin nanoparticle solution film are determined to a high extent by the interplay between the in-plane ordering of the solvent molecules in direct contact with the surfaces and the in-plane microscopic structure of the surface atoms.