Electroresponsive structuring and friction of a non-halogenated ionic liquid in a polar solvent: effect of concentration

Abstract

Neutron reflectivity (NR) measurements have been employed to study the interfacial structuring and composition of electroresponsive boundary layers formed by an ionic liquid (IL) lubricant at an electrified gold interface...

Micro- to Nano- and from Surface to Bulk: Influence of Halogen-Free Ionic Liquid Architecture and Dissociation on Green Oil Lubricity

“…This layer thickness compares well with the thickness of structured layers reported through neutron reflectance studies for similar molar concentrations of P-BMB and P-BMPP in different solvents on gold and silica substrates, respectively. 7,68 In addition, AFM experiments have shown the interfacial structuring of the pure P-BMB IL to be comparable for gold and silica surfaces. 80 The P-BEHP blend, on the contrary, shows the presence of ionic boundary films (about 2 nm) only at higher entrainment speeds (Figure 3a inset), whilst at lower speeds, it is almost indistinguishable from the BO case, suggesting that the P-BEHP ionic boundary films are less robust.…”

“…Such adsorbed layers have an overall benefit in terms of preservation of the surface composition, as well as the lubricant chemistry. Due to their ionic nature, ILs have been shown to be highly surface-active at charged and metallic interfaces and in some cases demonstrated to form ordered films, − providing a reduction in friction. − Although, under more severe contact conditions, e.g., due to an increase in load and/or temperature, some ILs have also been shown to break down, forming more reactive compounds, and in turn form sacrificial tribofilms on the lubricated surfaces. − …”

“…Moreover, at high temperatures and pressures, halogenated ILs have been demonstrated to readily undergo hydrolysis with ambient water, resulting in the formation of toxic and corrosive halides, , which can shorten the lifetime of machine components and contribute to enhanced wear or system failure. In the past decade, these concerns have driven the development of nonhalogenated ILs for tribological purposes. ,− ,, ILs with phosphate and phosphinate anions have emerged as the popular candidates, largely because of the presence of tribo-active phosphorus and their good miscibility with oils. ,,,− ,,,− ,− Phosphinate-based ILs have been reported to reduce friction on both the nano- and macroscale, in atomic force microscopy (AFM) and pin-on-disk experiments, respectively, when used in very low concentrations in oil. ,, Meanwhile, ILs with phosphate anions have shown improved friction and wear when used as additives in various oils. ,,,,, More recently, orthoborates have attracted attention as a new class of anions for lubrication applications and have been demonstrated to exhibit excellent friction reduction and wear protection, both as neat lubricants and as additives in oils. , When dispersed in other (more polar) solvents, they have also exhibited high surface activity, providing highly lubricious interfacial structures. − …”

The effect of anion architecture on the lubrication chemistry of phosphonium orthoborate ionic liquids

“…The changing technological landscape, with the rapid shift towards vehicle electrification and green energy production being the obvious examples, along with environmental concerns, has resulted in a need for lubricants with enhanced functionality such as electrical responsivity 11 – 14 . It is the role of chemists to facilitate the tribological advances by developing new formulations, sometimes even with new molecules, in an attempt to feed the industrial and societal demands.…”

The Effect of Anion Architecture on the Lubrication Chemistry of Phosphonium Orthoborate Ionic Liquid

“…10 The changing technological landscape, with the rapid shift towards vehicle electri cation and green energy production being the obvious examples, along with environmental concerns, has resulted in a need for lubricants with enhanced functionality such as electrical responsivity. [11][12][13][14] It is the role of chemists to facilitate the tribological advances by developing new formulations, sometimes even with new molecules, in an attempt to feed the industrial and societal demands.…”