Dispersion stability of ionic liquid-based graphene oxide

The work aims to investigate the dispersion stability of graphene oxide in ionic liquid and the influence factors and to verify the tribological properties. The modified DLVO theory was used to analyze the influence of the length of the alkyl side chain of the surfactant and the base carrier on the stability of the graphene oxide colloid. The results of theoretical analysis were assessed and verified according to experiments. The lubrication property of stable graphene oxide colloid was evaluated by reciprocating friction tester. The bare graphene oxide was unstable in ionic liquid since its potential curve always remained negative and the particles showed attractive force among each other. For the graphene oxide colloid system with modified surface, the interaction potential energies among particles were positively correlated with the chain length of the surfactant and base carrier. As the length of the alkyl side chain of the surfactant and the ionic liquid reached 9 and 6 respectively, the colloid showed the highest potential barrier value of 500 kT, thus realizing the stable dispersion. The results of the subsequent static experiment and UV-Vis absorption spectrum analysis were consistent with the theoretical analysis conclusion. The friction test showed that compared with pure ionic liquid, the stable ionic liquid-based graphene oxide presented better lubrication performance. The stability of ionic liquid-based graphene oxide colloidal system can be approximately predicted by the modified DLVO theory. The longer the alkyl side chain length of surfactant and ionic liquid is, the more stable the ionic liquid-based graphene oxide colloid will be. © 2019, Chongqing Wujiu Periodicals Press. All rights reserved.