Wear pressure induced structural changes of OLC nanoparticles and their regulated lubrication performances by mixing with NDs and GO

Here we report the tribological properties of nanosized onion-like carbon (OLC), OLC-nanodiamond (ND), and OLC-graphene oxide (GO) as additives in lubricant oil tested under different wear pressure. Under the wear pressure of 588 N of the four-ball testing, the 0.125 wt% addition OLC reduced the wear volume and the wear scar diameter by 36.29 % and 82.42 %. TEM characterization revealed structural changes in contour of the OLC particles after the wear testing. Pressure-induced agglomeration was seen for the OLC nanospheres, and the squeezed lattice changes resulted in formation of sp 3 diamond structure inside the spheres. These structural changes are directly related to the loading force. However, addition of the sp 3 NDs and sp 2 GO deteriorated the lubricating performances of the OLC-added lubricant oil.