Task–specific Ionic Liquids Based on Sulfur for Tribological Applications

Abstract

Ionic liquids (ILs) have been recently considered as potentially adequate lubricants for microelectromechanical and nanoelectromechanical systems (MEMS/NEMS) due to the specific features of these silicon based miniaturized devices. Aiming at the optimization of the lubrication of MEMS/NEMS, new ILs resulting from the combination of sulfur-containing anions (bis(2ethyl-1-hexyl) sulfosuccinate, [AOT], and ethylsulphate, [C 2 SO 4 ]) with ammonium, imidazolium or methylpyridinium based cations were prepared. Their tribological performance against silicon and steel was assessed with a nanotribometer and com-pared to that of other ILs based on the cation 1-ethyl 3methylimidazolium, [C 2 MIM]. Our results reveal that the presence of the anion [C 2 SO 4 ] is responsible for very low friction coefficients on silicon, meaning that these ILs may be considered as promising lubricants for MEMS/ NEMS. In contrast, the anion [AOT] did not lead to efficient lubricants for this type of systems. The results obtained on steel were not so impressive, although all the ILs based on [C 2 SO 4 ] presented better lubricant capacities than commercial oil.[a] J.

Imidazolium-based ionic liquids used as additives in the nanolubrication of silicon surfaces

“…The efficiency of ILs based on the anion EtSO 4 as pure lubricants was already reported in the literature [ 26 , 29 ]. However, to our knowledge, this is the first time that these ILs are successfully tested as additives to base lubricants.…”

“…ILs stand up as promising lubricants for this type of systems, all the more so since ILs are conductive liquids, leading to the minimization of the contact resistance between sliding surfaces, which is required for various electrical applications. Several authors have successfully tested pure ILs as lubricants for Si surfaces [ 22 – 26 ]. However, to our knowledge, the only reports on the efficient behavior of ILs as oil additives to lubricate Si surfaces were recently published by the group of T. Atkin [ 27 – 28 ].…”

“…They found favorable friction reduction with [C 2 OHMIM][Cl] being the least efficient IL. In contrast, promising results were obtained with [EMIM][EtSO 4 ], which were attributed to the presence of a stable tribofilm resulting from specific interaction between the [EtSO 4 ] anion and the silicon surface [ 26 , 29 ].…”

Picolinium‐Based Hydrophobic Ionic Liquids as Additives to PEG200 to Lubricate Steel‐Silicon Contacts

“…Silicon is another important material used in the manufacture of micro-and nano-electrical and mechanical systems (MEMS/NEMS), where the demand for conductive lubricants has increased. [21] Several research groups have been successfully testing the performance of pure ILs as lubricants for Si surfaces [22][23][24][25][26] but, to our knowledge, the only reports on the efficient behavior of ILs as oil additives to lubricate Si were recently published by the group of T. Atkin. [27,28] Sulfur-based organic salts were tested in our laboratory as additives in the base oil polyethylene glycol (PEG200) to lubricate Si substrates aiming at a future application in MEMS/ NEMS, which involve moving parts.…”

“…Silicon is another important material used in the manufacture of micro‐ and nano‐ electrical and mechanical systems (MEMS/NEMS), where the demand for conductive lubricants has increased . Several research groups have been successfully testing the performance of pure ILs as lubricants for Si surfaces but, to our knowledge, the only reports on the efficient behavior of ILs as oil additives to lubricate Si were recently published by the group of T. Atkin …”