Electrochemically exfoliated graphene and molybdenum disulfide nanoplatelets as lubricant additives

In this work, two different 2D materials, molybdenum disulfide nanoplatelets (MSNP) and graphene nanoplatelets (GNP), prepared by electrochemical exfoliation, were used as additives to prepare nanolubricants. The tribological behaviour of the nanolubricants was evaluated under two configurations (pure sliding and rolling/sliding) using two different tribometers: an Universal Macro Materials Tester (UMT-3) and a Mini Traction Machine (MTM2). Wear volume was determined, after the sliding tests, in a confocal microscope (Leica DCM 3D) and the worn surface was analyzed by Scanning Electron Microscopy (SEM), Energy Dispersive Spectroscopy (EDS) and Raman microscopy. Lubrication mechanisms of GNP and MSNP dispersed in an engine oil for improving its antifriction and antiwear capabilities are proposed. The traction coefficient determination was performed at a 50% of slide-to-roll ratio and at different temperatures. The results showed that the nanolubricants formulated with both types of additives, in their lowest concentration, improved friction and wear in sliding tests, compared to neat engine oil. In addition, only the nanolubricants with the MSNP nano additive at loadings of 0.05 and 0.2 wt% showed friction reductions compared to the commercial engine oil under the rolling/sliding testThe following institutions and grants are acknowledged for funding this research: Ministry of Economy and Competitiveness of Spain (grant number: ENE2017-86425-C2-2-R project), Foundation for the Promotion of Applied Scientific Research and Technology in Asturias (grant number: IDI/2018/000131), and Xunta de Galicia in Spain (grant numbers: AEMAT ED431E 2018/08 and GRC ED431C 2020/10)S