The Effects of Single-Walled Carbon Nanotubes and Ionic Liquids in Reduction of Friction and Wear

Abstract

A significant amount of energy dissipates from frictional losses of moving components in machinery and devices in industry. This contact friction leads to the wear and eventual failure of industrial mechanical components over extended time through adhesion, abrasion, fatigue, or corrosion. Frictional losses could be mitigated by utilizing more effective lubricants, which would allow the translating surfaces to slide over one another more fluently. There is reason to study eco-friendly alternatives over traditional lubricants to reduce negative impact to the environment. The implementation of Ionic Liquids (ILs) as additives to oil-based lubricants is a development in tribology with the potential to lower the friction coefficient and reduce wear. When carbon nanotubes are dispersed into these ionic liquids, the reduction of losses due to friction and wear can be even greater. In this experiment, single-walled carbon nanotubes (SWCNTs) of four concentrations, 0 wt.%, 0.01 wt.%, 0.02 wt.%, and 0.03 wt.% were dispersed in a room temperature ionic liquid, Trihexyl(tetradecyl)phosphonium bis(2,4,4-trimethylpentyl) phosphinate, or [THTDP][Phos] for short, to form four homogeneous mixtures. Then, each mixture was added in 1 wt.% to a base vegetable oil. Friction tests were also conducted with pure vegetable oil for comparative purposes. The experiments consist of a pin-on-disk rotational tribometer and a ball-on-flat reciprocating tribometer both applying a steel-steel (AISI 52100) contact to evaluate the lubricating ability of combining SWCNTs and ILs as lubricant additives. The load, speed, wear radius, sliding distance, and duration of the experiment were held constant to isolate lubrication as the experimental parameter. Optical microscopy (OM), thermogravimetric analysis (TGA), and viscometer analysis were utilized after experimentation to analyze and discuss the wear mechanisms of the worn surfaces. Results differed between rotational and translational experiments, with the rotational results yielding a decrease of 14.21% in wear loss with the VO+1%[THTDP][Phos] lubricant. The translational results yielded a continuous decrease in wear loss with the increase in SWCNT wt.%.