Nano/Microtribological Properties of Ultrathin Functionalized Imidazolium Wear-Resistant Ionic Liquid Films on Single Crystal Silicon

Abstract

Ionic liquids (ILs) are considered as a new kind of lubricant for micro/nanoelectromechanical system (M/ NEMS) due to their excellent thermal and electrical conductivity. However, so far, only few reports have investigated the tribological behavior of molecular thin films of various ILs. Evaluating the nanoscale tribological performance of ILs when applied as a few nanometersthick film on a substrate is a critical step for their application in MEMS/NEMS devices. To this end, four kinds of ionic liquid carrying methyl, hydroxyl, nitrile, and carboxyl group were synthesized and these molecular thin films were prepared on single crystal silicon wafer by dipcoating method. Film thickness was determined by ellipsometric method. The chemical composition and morphology were characterized by the means of multitechnique X-ray photoelectron spectrometric analysis, and atomic force microscopic (AFM) analysis, respectively. The nano-and microtribological properties of the ionic liquid films were investigated. The morphologies of wear tracks of IL films were examined using a 3D non-contact interferometric microscope. The influence of temperature on friction and adhesion behavior at nanoscale, and the effect of sliding frequency and load on friction coefficient, load bearing capacity, and anti-wear durability at microscale were studied. Corresponding tribological mechanisms of IL films were investigated by AFM and ball-on-plane microtribotester. Friction reduction, adhesion resistance, and durability of IL films were dependent on their cation chemical structures, wettability, and ambient environment.

Semi-Empirical Molecular Modeling of Ionic Liquid Tribology: Ionic Liquid–Hydroxylated Silicon Surface Interactions

“…One observes a correlation between frictional coefficients and the computed D f H's of the various IL (IL)-silicon surface complexes [11], similar to that obtained for IL-silicon nitride and IL-Al-steel alloys [16]. In the second part, this approach is extended to the interaction of dicationic ILs (Figs.…”

“…This latter solubility property of RTILs makes them ideal solvents for catalysis as they can be recycled, thus becoming ideal candidates for numerous commercial chemical reactions [1]. In recent years, RTILs have shown great potential as candidates for lubrication processes [2][3][4][5][6][7][8][9][10][11][12][13][14][15].…”

“…Several studies of ionic liquid (IL) tribology [2][3][4][5][6][7][8][9][10][11][12][13][14][15] have tested various surfaces including Al-steel, steel-steel, steel-copper, steel-SiO 2 , Si 3 N 4 , Si 3 N 4 -SiO 2 , and silicon wafers. These previous results led to a semi-empirical modeling study of the interactions of ionic liquids (ILs) with metal and silicon nitride surfaces [16].…”

“…The first part includes the modeling of the interactions of four imidazolium chloride ILs ( Fig. 1) with hydroxylated silicon surfaces [11]. These four 1-methyl-3-substituted imidazolium chloride (MEIMRÁCl) ILs in Fig.…”

Tribological Behaviour of PVD Coatings Lubricated with a FAP− Anion-Based Ionic Liquid Used as an Additive

“…Ionic liquids have been studied as lubricants of a series of contacts over the last decade, particularly steel-steel [9][10][11][12][13][14][15], lightweight materials (aluminium and silicon alloys) [16][17][18][19][20], various engineering surfaces, like nanocrystalline nickel coating [21], phosphor bronze [22], electrodeposited Ni/Si 3 N 4 composition coating [23], 1Cr18Ni9Ti stainless steel modified by plasma nitriding [24] and many friction coefficient and wear reduction of the traditional additive ZDDP in the same weight proportion. Hernández et al [50] analysed the same [(NEMM)MOE][FAP] ionic liquid as a pure lubricant and as an additive (PAO 6 as base oil) within the lubrication of three PVD coatings (TiN, CrN and DLC).…”