Physicochemical and tribological properties of gemini-type halogen-free dicationic ionic liquids

Abstract

A series of new halogen-free dicationic ionic liquids (ILs) with different alkyl chain lengths were prepared, and the relationship between the alkyl chain length, physicochemical and tribological properties of ILs, and their role as neat lubricant for steel-steel friction pairs, was investigated. Evaluation of stability during hydrolysis and copper strip corrosion test results show that synthetic ILs are stable and not corrosive to metal contacts, due to the halogen-free anions. The friction and wear test results indicate that ILs with long alkyl chains have excellent friction-reducing and anti-wear properties, especially at high temperatures. Based on the surface three-dimensional (3D) profiles, electrical contact resistance, scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), and the X-ray photoelectron spectrometry (XPS) analysis of the worn surfaces of steel discs, we can conclude that the efficiency of ILs is due to the formation of high quality tribofilms that consist of both tribochemical reaction and ordered absorption films.

A review of advances in tribology in 2020–2021

“…ILs can increase the stability of lubricant additives [16], such as NiAl particles and trihexyl(tetradecyl)phosphonium cation [17], and improve their tribological performance. ILs can exhibit excellent lubricating performance under different working condition, e.g., under extreme temperature [18], electric field [19], etc.…”

“…Zhao et al [230] proposed that the excellent tribological properties under high temperature are attributed to the formation of physical adsorption Fig. 18 Comparison of the tribological properties of different polymer matrices and different fillers [227]. Reproduced with permission from Ref.…”

Influence of alkyl chain length on the tribological performance of choline ionic liquids as water-based lubricating additives under electric field conditions

“…Developing green lubricants are imminent. [15][16][17] Presently, a lot of research on environmentally friendly ionic liquids [18][19][20][21][22][23][24][25] is ongoing both domestically and internationally. Fang et al[26] synthesised four new oil-mixed proton ionic liquids containing different fatty acid anions.…”

Applications of carbon quantum dots in lubricant additives: a review

“…Among them, the friction-reducing and anti-wear additives play an indispensable role in alleviating the friction and wear of the contact area by forming a physical adsorption/deposition film and/or tribochemical reaction film on the rubbing surfaces [28][29][30][31][32][33][34]. The traditional friction-reducing and anti-wear additives are usually composed of organic polar materials, such as organic molybdenum compounds [35][36][37], polymers [38], alcohols [39], esters [40][41][42], amine compounds [43], organic salts [44], ionic liquids, and their derivatives [45][46][47][48][49][50]. The strong polarity allows them to form neat adsorption films on the metallic rubbing surfaces to reduce the friction and wear of friction pairs.…”