Understanding the Friction of Nanometer-Thick Fluorinated Ionic Liquids

Abstract

Ionic liquids (ILs) show promise as lubricants for nano- and microelectromechanical systems (NEMS/MEMS) and hard disc drives (HDDs). When deposited on solid substrates as nanometer-thick films, these liquids can exhibit a solid-like layering structure, which makes them ideal as lubricants. Moreover, ILs are “designer” materials with many possible molecular structures and tunable properties. In this work, we have experimentally investigated the friction of various nanometer-thick fluorinated ILs on a silica surface using a nanotribometer. We found that surface tension has a significant effect on the friction. When the surface tension of ILs is low, ILs wet the silica surface, and the friction is low. However, when the surface tension is high, ILs form droplets and do not wet the silica surface, which results in higher friction. The effect of moisture at the interface has also been investigated, and the results suggested that water promotes the surface charging of silica, which induces more ordered cation/anion layering and thus reduces the friction. The finding here is critical in designing novel nanometer-thick IL lubricants.

Nanometer-Thick Fluorinated Ionic Liquid Films as Lubricants in Data-Storage Devices

“…The surface tension of Z-tetraol is 22.4 mN/m, while the surface tension of [Bmim]­[FAP] is 32.4 mN/m from pendant drop analysis. The higher surface tension of the IL can be attributed to fewer CF x groups in its chemical structure . On the other hand, the bonding of the IL to the substrate was much weaker than that of the PFPE.…”

“…The higher surface tension of the IL can be attributed to fewer CF x groups in its chemical structure. 18 On the other hand, the bonding of the IL to the substrate was much weaker than that of the PFPE. Figure 6 shows the difference between the thickness of the nanometer thick films before and after Vertrel Vertrel washing was operated following similar procedures to dip-coating except using coated samples and pure Vertrel instead of bare COC and solutions.…”

“…Many commercially available ILs contain fluorinated segments in their anions. Such fluorinated ILs have low surface tension, which induces promising tribological performance and corrosion protection. , Most ILs are also more cost-effective than PFPEs. Moreover, as a group of “designer materials”, the molecular structures of ILs can be readily tailored by manipulating the ion pairs based on the desired molecular sizes and physicochemical properties.…”

Insight into the Effect of TDMs on the Tribological Behaviors of the Ionic Liquid Composite Films

“…Good lubrication has become a crucial issue for improving performance reliability and reducing the energy consumption of the moving parts, and a solid lubricant on the contact surface of moving parts has become an important choice. Since the initial report in 2001 [4], ionic liquids (IL) with special configuration and outstanding tribological performance have evoked a great deal of attention in the area of lubricating applications [5][6][7][8][9][10].…”

Effects of magnetic ionic liquid as a lubricant on the friction and wear behavior of a steel-steel sliding contact under elevated temperatures

“…With the continuous progress of industrial technology, newly developed lubricants need to meet more and more stringent requirements for mechanical properties and lubricating performance [1][2][3]. Besides excellent load-bearing capacities, good friction-reducing, and antiwear abilities, they also need to exhibit self-repairing capabilities and environmental acceptance.…”