Ionic Liquids in Tribology

Abstract

Current research on room-temperature ionic liquids as lubricants is described. Ionic liquids possess excellent properties such as non-volatility, non-flammability, and thermo-oxidative stability. The potential use of ionic liquids as lubricants was first proposed in 2001 and approximately 70 articles pertaining to fundamental research on ionic liquids have been published through May 2009. A large majority of the cations examined in this area are derived from 1,3-dialkylimidazolium, with a higher alkyl group on the imidazolium cation being beneficial for good lubrication, while it reduces the thermo-oxidative stability. Hydrophobic anions provide both good lubricity and significant thermo-oxidative stability. The anions decompose through a tribochemical reaction to generate metal fluoride on the rubbed surface. Additive technology to improve lubricity is also explained. An introduction to tribology as an interdisciplinary field of lubrication is also provided.

Ionic liquids as an additive in fully formulated wind turbine gearbox oils

“…Accordingly good antiwear properties, hydrolytic stability and hydrophobicity of the [NTf 2 ] anion reported by Minami et al [16,30]. This paper studies the effectiveness of using two ionic liquids …”

“…Different FAP-anion based ILs have been studied both as additive and as a neat lubricant for different materials pairs exhibiting excellent friction and wear reducer behaviour [20][21][22][23][24][25][26]. Some review papers [29][30][31][32] have detailed the advantages of using ILs in tribology, their thermal and oxidative stability, and their tribochemical reactions.…”

Isoconversional kinetic analysis applied to five phosphonium cation-based ionic liquids

“…A lot of researches have been published concerning the use of ionic liquids as lubricants since 2001 [29], proving their remarkable potential for this purpose [4,6,[30][31][32]. At the beginning, imidazolium-based ionic liquids with [PF 6 ] and [BF 4 ] anions were widely used [33][34][35].…”

Tribo-Chemistry of Phosphonium-Derived Ionic Liquids

“…Since then, there have been numerous reports on similar applications have been published in international tribology journals. Thus far, the relationship between the chemical structure and the tribological properties of RT-ILs has been fundamentally studied [9][10][11]; it has been observed that hydrophobic anions (e.g., TFSA) afforded better tribological properties to RT-ILs than the hydrophilic anions (e.g., BF 4 ) [12,13]. Higher alkyl groups in imidazolium cations are instrumental in improving the tribological properties of a compound.…”

“…However, in tribology, the main anions under consideration are BF 4 , PF 6 , and TFSA. Most literatures on cationic moieties deal with imidazolium derivatives [9]. From a chemical perspective, alkylimidazolium cations are versatile building blocks of cationic moieties having bulky and asymmetrical skeletons.…”