Multi-Phase Friction and Wear Reduction by Copper Nanopartices

Abstract

Finely dispersed copper nanoparticles were added as an additive to fully-formulated engine oils. The copper additive was in colloidal form, with an inner core of Cu 2+ atoms covered by surfactants to form stable reverse micelles that are completely dispersible in the base oil. The tribological process to form protective films at the metal surface is comprised of three phases. Phase I can be considered a physical process involving the build-up of polar molecules by absorption to produce a friction modifier film, whereas phases II and III have to be treated as mechanochemical processes comprising a combination of redox reactions and a third body formation. The tribological performance was investigated using atomic force microscopy, a microtribometer, a pin-on-disk tribometer in combination with continuous and high-resolution wear measurements with radionuclide technique, and high pressure stressing in a thrust roller bearing test rig. In addition, the nanostructure of the additive was characterized by atomic force microscopy. Finally, the chemical composition of the metal surface was analyzed using photoelectron spectroscopy.

Influence of tribology on global energy consumption, costs and emissions

“…As a result of concerted efforts, very low friction, even as low as a coefficient of friction of 0.005, has been measured in the presence of friction modifier additives like glycerol mono-oleate (GMO) or pure glycerol when lubricating tetragonal amorphous carbon coatings [33][34][35]. Nanomaterials with very promising tribological properties under investigation are carbon-based additives including nano-diamonds, onion-like carbons, carbon nanotubes, graphene, graphite as well as some inorganic fullerenes of transition metal dichalcogenides, like MoS 2 and WS 2 , and copper, polymeric and boron-based nanoparticles [36][37][38][39][40][41][42][43].…”

Metal-containing nanomaterials as lubricant additives: State-of-the-art and future development

“…Cu NPs can deposit and fill up micropits and grooves on steel friction surfaces under a higher load, and consequently they significantly reduce steel pair wear by self-repairing worn surfaces [80]. One should note triangular copper nanoplates prepared with cetyltrimethylammonium bromide as the capping agent [82]. As an additive for lubricants, nanoplates are responsible for the formation of a film deposit at the interface of a friction pair and a 12% drop in COF of the lubricant and an 82.2% drop in wear loss.…”

Investigating Efficacy of Cu Nano‐Particles as Additive for Bio‐Lubricants

“…The additives namely the ZDDP and oleic acid functionalized Cu nano‐particles when interact with steel surfaces in four ball tribo‐testers, the Cu and Zn particles get adsorbed on the nascent iron on tribo surface. These Cu and Zn particles get adsorbed on the tribo surface and form a thin and self‐lubricating tribo‐film . In 4 ball tribo experiments this film between the tribo contacts is in dynamic equilibrium where layers of Cu or Zn atoms gets replaced by new particles that sustains tribo‐performance and improve their anti‐friction and anti‐wear properties.…”

“…These Cu and Zn particles get adsorbed on the tribo surface and form a thin and self-lubricating tribo-film. [12][13] In 4 ball tribo experiments this film between the tribo contacts is in dynamic equilibrium where layers of Cu or Zn atoms gets replaced by new particles that sustains tribo-performance and improve their anti-friction and anti-wear properties. The lubrication mechanism of the additives is shown in the pictorial form in Figure 7.…”