Tribological Properties of Ultra-Thin Functionalized Polyethylene Film Chemisorbed on Si with an Intermediate Benzophenone Layer

Abstract

In this study, an ultra-thin (*20 nm) functionalized polyethylene (fPE) film is successfully attached to Si substrate via a reactive benzophenone (Ph 2 CO) layer. The presence of fPE promotes wear durability of Si/Ph 2 CO/fPE to 1,000 cycles compared with 100 cycles for Si/Ph 2 CO and nearly zero wear life for bare Si in a ballon-disk (4-mm-diameter Si 3 N 4 ball) wear test under 40 mN applied normal load and 500 rpm sliding speed. As an enhancement to the wear life, perfluoropolyether (PFPE) is applied as a top mobile lubricant layer coated onto Si/Ph 2 CO and Si/Ph 2 CO/fPE. A significant improvement in the wear durability is observed as Si/Ph 2 CO/PFPE fails at 250,000 cycles and Si/Ph 2 CO/fPE/PFPE does not fail until one million cycles. Si/Ph 2 CO/fPE/PFPE can withstand a minimum applied load of 150 mN at a sliding speed of 0.052 ms -1 without failure, providing a PV (pressure x velocity) limit of greater than 106.6 MPa ms -1 .

Wetting behavior of textured silicon surfaces- an experimental study

“…The wetting of the solid surface by the liquid behavior depends on two main properties of the solid surface under study: the surface energy of the top molecular layer and its surface morphology. Certain studies mention that hydrophobicity can be achieved only by modifying the chemical composition by lowering surface energy [2][3][4][5][6][7][8][9][10]. However for superhydrophobicity, surface morphology has a significant effect on wettability [11] where the air gets trapped in between the liquid and the rough surface.…”

Transforming organic molecular films into carbon films as solid lubricants

“…[1][2][3] Though carbon lms fabricated by vapor deposition have superior resistance to wear and strong adhesion to substrates, they are still difficult to meet the demand of nano-scale thickness for sophisticated moving parts with many edges and corners. 4,5 Therefore, many organic lms with low stiction and low friction prepared by solution-based approaches have been explored for MEMS/NEMS, such as ultrathin polymer lms, 6 nanocomposite molecular layers, 7,8 and self-assembled monolayers (SAMs). 9,10 However, their anti-wear ability and adhesion to silicon substrates are much worse than carbon lms, and their thicknesses are also difficult to regulate as required.…”

Ultrathin PFPE Film Systems Fabricated by Covalent Assembly: An Application to Tribology

“…However, the thickness of the UHMWPE film was relatively high and therefore restricted its tribological application for micro-components made out of Si [29]. In another study, a functionalized polyethylene was used as an intermediate layer (with a thickness of 15 nm) between benzophenone-modified Si and PFPE and it has shown improved tribological properties [30]. However, for certain applications, there arises a need to further reduce the overall thickness of polymer layers without compromising the tribological performance.…”