The pH-dependent structural and tribological behaviour of aqueous graphene oxide suspensions

In this study, the tribological characteristic of aqueous dispersions of single-layer graphene oxide (GO) sheets was assessed as a function of pH. The flexible and large GO sheets were broken down and chemically reduced upon increasing the pH from 3.10 to 9.70. By using the 0.06 wt% GO suspension, the noise and vibration in tribological tests were eliminated, at the same time, the coefficient of friction (COF) and wear mark radius were reduced by 44.4% and 17.1%, respectively, compared with baseline water. While the increase of pH of the GO suspensions increased COF and wear significantly. The difference of the lubricating mechanism of the GO suspensions was attributed to the change of morphological and physicochemical properties of the GO sheets.