The effect of the number of branched hydrocarbon molecules on boundary lubrication of ZnO nanofluids by using molecular dynamics simulation

In this paper, the effect of branched hydrocarbon molecules, i.e., polymethylene olefins (PAO), on the boundary lubrication of ZnO nanofluids is investigated using large-scale molecular dynamics (MD) simulations. The film structure and friction of the lubricated film on the atomic scale are discussed, and the slip distance of the iron wall is calculated. The results show that the nanofluid forms a layered structure under stronger liquid-solid interactions; the higher the number of PAO branches, the higher the number of atoms between the contact surfaces, which significantly reduces the friction force in the event of inhomogeneous contacts; the higher the number of PAO branches, the higher the number of atoms between the contact surfaces, which significantly reduces the friction force in the case of inhomogeneous contact, with a maximum reduction of about 95%; as the number of PAO branches increases, the wall slip distance of the system increases.