A series of 1-alkyl-3-ethylcarboxylic acid imidazolium chloride ([AEImi][Cl]) ionic liquids was synthesized and evaluated as a new kind of lubricant for microelectromechanical system (MEMS). In this research, novel molecular thin ionic liquid films (ILs) with various bonding percentages were prepared with different annealing temperatures and times. Film wettability was determined by measurement of contact angle and thickness with the ellipsometric method. The chemical composition, structure and morphology were characterized by the means of multi-technique X-ray photoelectron spectrometric, and atomic force microscopic analysis, respectively. The nano- and microtribological properties of the ionic liquid film were investigated. The morphologies of wear tracks of IL films were examined using a 3D non-contact profilometer. The influence of chain length on friction in nano-scale, and the effect of bonding percentage and sliding frequency on friction coefficient, carry-bearing capacity and durability in micro-scale were studied. Data are compared to the perfluoropolyether lubricant Z Dol. The [AEImi][Cl] ionic liquid films with appropriate bonding percentage exhibited comparable load-bearing capacity and durability than Z Dol 3800 at thickness level of several nanometers. Therefore, the [AEImi][Cl] ionic liquid film shows strong potential applications involving the lubrication and protection of MEMS.
Yufei Mo,Bo Yu,Wenjie Zhao,Mingwu Bai.
Applied Surface Science,255,5,Part 1,2276-2283(2008)