Tribological enhancement using Mn3O4-Graphene nanocomposites as additives for potential transmission fluids of electric vehicles

Abstract

This research reports the antifriction and antiwear properties of Mn3O4-Graphene nanocomposites (Mn3O4-G) as additives of a paraffinic base oil commonly used in the formulation of electric vehicles transmission oils, G-III base oil. Four G-III base oil nanodispersions have been designed, G-III base oil + 0.025 wt% Mn3O4-G, G-III base oil + 0.050 wt% Mn3O4-G, G-III base oil + 0.075 wt% Mn3O4-G and G-III base oil + 0.100 wt% Mn3O4-G, to know the optimal concentration of nanoadditive. Tribological experiments were carried out with these nanolubricants and with neat G-III base oil at pure sliding conditions under a working load of 9.43 N. All tested nanolubricants led to similar friction coefficients in comparison to that obtained using G-III base oil. Tribological specimens tested with formulated nanolubricants revealed less wear than that obtained with G-III base oil, obtaining the greatest wear reduction using the G-III base oil + 0.075 wt% Mn3O4-G nanolubricant, with reductions of 25, 50 and 64% in wear scar diameter, maximum depth and transversal area, respectively. Moreover, by means of confocal Raman microscopy and roughness evaluation of worn tribological specimens, it was concluded that synergetic effect, tribofilm formation and rolling mechanisms happen