Ionic Liquids Interactions with Materials Surfaces Applications in Tribology and Nanotechnology

Abstract

The extraordinary combination of high thermal stability, low volatility and the possibility of tailoring the physical and chemical properties of ionic liquids (ILs) by modifying their molecular features such as the length and nature of the cation lateral chains and the anion size and composition, has open the field of application of these green ordered fluids.ILs have shown their ability to provide effective lubrication with very low friction coefficients and wear rates under conditions for which the currently used lubricating fluids fail. These conditions cover strategic technologies such as aerospace, microelectronics and nanotechnology applications.At the present moment, there exist no liquid lubricants for high temperature, high vacuum and cryogenic conditions. We have determined the lubricating ability of ILs under extreme temperature conditions.We have also determined the conditions for the formation of tribocorrosion reaction products at metal-metal and metal-polymer interfaces. In the case of fluorine or phosphorus-containing imidazolium ionic liquids, formation of metallic fluorides and phosphates at the contact surfaces is the determining wear mechanism step.The surface interactions of imidazolium room temperature ILs have been studied in a variety of materials in sliding contact under variable conditions, both as neat lubricants and as additives of conventional basestocks.The ability of ILs molecules to interact with surfaces has also been explored in nanotechnology applications. It is well known that the use of ILs as solvents in the synthetic route, allows the control of size and shape of a variety of nanoparticles. We have developed new polymer/IL/nanoparticle nanocomposites where the size, morphology and distribution of the nanoparticles are controlled by surface interactions with IL molecules.

The Lubrication Ability of Ionic Liquids as Additives for Wind Turbine Gearboxes Oils

“…In the last decade, the use of ionic liquids (ILs) has attracted attention in the tribology community as potential lubricants and lubricants additives for challenging contacts [8][9][10][11]. ILs, also known as fused salts and molten salts, are ionic compounds with meting points lower than 100˝C.…”

Tribological Characterization of Several Silicon-Based Materials Under Ionic-Liquids Lubrication

“…In this case, it can be inferred that the relatively low COFs under the lubrication of Ions 2 and 3 can be partly ascribed to the formation of lubricating tribo-layers. It was also argued that surface ordering of the IL lubricant molecules was present, and longer alkyl chains on the imidazolium ring could produce better lubrication performances [36][37][38][39][40].…”

Self-lubricating, wear resistant protic ionic liquid-epoxy resin

“…Room-temperature ionic liquids (ILs) [11,12] contain bulk organic cations and organic or inorganic anions and show a unique combination of properties such as their low volatility, non-flammability, and their high thermal stability which are most relevant for tribological applications. ILs have shown excellent tribological performance, not only in lubrication of metal alloys and ceramic materials under severe sliding conditions [13][14][15][16][17][18][19][20][21][22][23][24][25], but also in the very difficult task of achieving the reduction of friction coefficients and wear rates of thermoplastic polymers and epoxy resins, where they have been used both as external lubricants and as additives [26][27][28][29][30][31][32][33][34][35][36][37][38][39][40]. Ionic liquids are also making an increasing impact in the field of polymer science, in particular on the development of new epoxy networks and composite materials by acting as curing agents, plasticizers, and as dispersants of nanophases in the epoxy matrix [35][36][37][38][39].…”

“…Several research groups are currently working in the study of halogen-free ILs which could substitute the conventional ones [30,41,42]. We have recently developed new lubricants and additives based on protic ionic liquids (PILs), in particular protic ammonium carboxylate salts, some of which show outstanding lubricating behaviour [25,[41][42][43]. The main objective of the present study is to develop new epoxy resin protic ionic liquid hybrid materials in a simple way, and to determine the effect of the additive on the properties and tribological performance of the polymer, in particular, to prevent the severe surface damage and high friction coefficients of brittle epoxy resin materials.…”