Tribochemistry effect on the friction reduction of Al 2 O 3 /ethylene glycol composite lubricant between steel self‐mated tribosystem

In our previous work, we find that the ethylene glycol (EG) is transferred to amorphous carbon or graphene during sliding under the effect of the tribochemical reactions; herein, in this work, we control the concentration of the modified Al 2 O 3 nanoparticles in the EG solution in order to modulate the tribological properties of the tribosystem sliding in the mixed lubricant consisting of the modified Al 2 O 3 nanoparticles and EG. The tribological tests show that the concentrations of the modified Al 2 O 3 nanoparticles ranging from 0 to 1.0 wt% in the mixed lubricant are helpful for obtaining low wear rate due to the formation of graphene‐like materials induced by tribochemical reactions. On the other hand, when the concentration reaches 1.5 wt.%, the tribosystem exhibits high coefficient of friction (COF) and wear rate, which is attributed to the formation of reunited groups consisting of the modified Al 2 O 3 nanoparticles and graphene‐like materials. This investigation should give a positive guidance for the design of the mixed lubricant with excellent lubrication properties.