Finely dispersed copper nanoparticles were added as an additive to fully-formulated\nengine oils. The copper additive was in colloidal form, with an inner core of Cu2+ atoms covered\nby surfactants to form stable reverse micelles that are completely dispersible in the base oil.\nThe tribological process to form protective films at the metal surface is comprised of three phases.\nPhase I can be considered a physical process involving the build-up of polar molecules by\nabsorption to produce a friction modifier film, whereas phases II and III have to be treated as\nmechanochemical processes comprising a combination of redox reactions and a third body formation.\nThe tribological performance was investigated using atomic force microscopy, a microtribometer,\na pin-on-disk tribometer in combination with continuous and high-resolution wear measurements\nwith radionuclide technique, and high pressure stressing in a thrust roller bearing test rig. In addition,\nthe nanostructure of the additive was characterized by atomic force microscopy. Finally, the chemical\ncomposition of the metal surface was analyzed using photoelectron spectroscopy.
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