Simultaneous chemical reduction and surface functionalization of graphene oxide for efficient lubrication of steel–steel contact
An improved method for the preparation of graphene oxide (GO) and further exfoliation of GO to graphene is described. Simultaneous surface functionalization and reduction of GO with octadecylamine (ODA) was also achieved without any further reducing agents. The structural aspects of GO, GO-ODA and graphene were analyzed by UV-Vis spectrometry, infra red spectroscopy, Raman spectroscopy and transmission electron microscopy. The wetting behavior of the functionalized particles were accessed by water contact angle measurements. The particle sizes in the oil suspensions which is actually fed to contact for lubrication were estimated using dynamic light scattering technique. Tribological performances and load bearing capacity of the particle suspensions were tested under two different pressure regime on a rotational tribometer with pin/ball-on-disc set up. The increase in hydrophobicity in GO-ODA helped the particles to work much better in low load condition due to the presence of long hydrocarbon chain as a shield between the contact. However the hydrophilic GO was found to perform better in the high load regime due to its adhesion to the substrate when squeezed under high pressure. The work focuses on lubrication mechanism of chemically functionalized graphite particles as the load bearing candidates for efficient lubrication of sliding contact.