Gradation, Dispersion, and Tribological Behaviors of Nanometric Diamond Particles in Lubricating Oils

Abstract

To improve the dispersion characteristics of nanometric diamond in lubricating oil and optimize its tribological properties, the gradation, dispersion, and tribological behaviors of nanometric diamond particles in lubricating oils were studied in this chapter. The dispersion characteristics of modified nanometric diamond in lubricating oils were observed by centrifugal and static methods. The four-ball tribometer was performed to study the tribological properties of the modified nanometric diamond as additive in hydraulic fluid. The morphology, particle size, surface functional groups, and structure composition of diamond powders before and after modification were analyzed and compared by means of FE-SEM, Zeta, FTIR, and XRD. Scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), and Raman spectroscopy were selected to characterize the worn scar surface after rubbing process. The results showed that the modified nanometric diamond particle was fined, the surface functional group number was increased, and the steric effect in lubricating oil was produced, so that it exhibited excellent dispersion stability. Modified nanometric diamond as lubricating additives has good anti-wear and friction-reducing performance in hydraulic oil is mainly attributed to a large amount of small nanometric diamond particles, some fined particles fill and repair the rough surfaces of the friction pairs, and part of them enters the interface between the friction pairs to form rolling effect, which improves the anti-wear and friction-reducing properties.