Tunable lubricity of aliphatic ammonium graphite intercalation compounds at the micro/nanoscale

Graphite is consisted of a series of stacked graphene layers bonded by weak van der Waals forces, possesses many fascinating electronic and mechanical properties. The presence of intercalates between graphene layers can significantly modify the interlayer interaction energy, and then potentially tune the lubrication performance. Constant potential reduction method was used for electrochemical intercalation of tetraalkylammonium bromide salts (R4N+, R = CH3/C5H11/C8H17) and ionic liquids (ILs) into graphite foils and powders. The coefficients of friction (COFs) of the synthesized GICs are almost one third of that of the pristine graphite at the microscale. Nanoscale frictional measurements on the mechanically exfoliated GIC surface suggest that the reduction of friction after intercalation is primarily due to the decrease of interfacial shear strength rather than the reduced interaction energy between expanded interlayers. On the basis of these results, it has been demonstrated the feasibility that the frictional behaviors of graphite could be modulated by intercalation of chemical substances, giving rise to promising solid-liquid composite lubricant systems.

The frictional properties of the synthesized graphite intercalation compounds at the micro- and nano-scales proved that the frictional behaviors of graphite could be modulated by intercalation of chemical substances, giving rise to promising solid-liquid composite lubricant systems.247