Effect of Ellipsoidal Particle Shape on Tribological Properties of Lubricants Containing Nanoparticles

Abstract Adding nanoparticles can significantly improve the tribological properties of lubricants. However, there is a lack of understanding regarding the influence of nanoparticle shape on lubrication performance. In this work, the influence of diamond nanoparticles (DNPs) on the tribological properties of lubricants is investigated through friction experiments. Additionally, the friction characteristics of lubricants regarding ellipsoidal particle shape are investigated using molecular dynamics (MD) simulations. The results show that DNPs can drastically lower the lubricant's friction coefficient μ from 0.21 to 0.117. The shearing process reveals that as the aspect ratio ( α ) of the nanoparticles approaches 1.0, the friction performance improves, and wear on the wall diminishes. At the same time, the shape of the nanoparticles tends to be spherical. When 0.85 ≤ α ≤ 1.0, rolling is ellipsoidal particles' main form of motion, and the friction force changes according to a periodic sinusoidal law. In the range of 0.80 ≤ α < 0.85, ellipsoidal particles primarily exhibit sliding as the dominant movement mode. As α decreases within this range, the friction force progressively increases. The friction coefficient μ calculated through MD simulation is 0.128, which is consistent with the experimental data.