STM, QCM, and the Windshield Wiper Effect:  A Joint Theoretical−Experimental Study of Adsorbate Mobility and Lubrication at High Sliding Rates

Abdelmaksoud, M.; Lee, SM; Cw, Padgett; Irving, Douglas L.; Dw, Brenner; Krim, J.

doi:10.1021/la061797w

Cited by 15 publications

(13 citation statements)

References 15 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…In real applications, in oil environments, the nanodiamonds would be able to perform the special role of enabling film formation and replenishing it continuously from the fresh supply of oil while the tribo-pairs are in action. The rate of film formation, however, must not be exceeded by the wear rate [34].…”

Section: Discussionmentioning

confidence: 99%

Synergistic Effect of Nanodiamond and Phosphate Ester Anti-Wear Additive Blends

et al. 2018

View full text Add to dashboard Cite

Nanodiamonds are known to improve tribological performance when added to lubricants, but their impact on additives that may already be present in the lubricant is poorly documented. Here, we report on a study of their effects on thermal reaction films formed from tricresyl phosphate (TCP) on Fe substrates immersed in a dibasic ester basestock when blended with TCP. Thermal reaction film formation temperatures were recorded in-situ by monitoring the reaction film formation on both Fe and air baked Fe surfaces using a quartz crystal microbalance (QCM). The nanodiamonds were found to raise the thermal reaction film formation temperature by 18 • C, possibly by raising the activation energy for the reaction, but they were not observed to affect the thickness or rate of formation of the films. The nanodiamonds, moreover, were observed to trigger thermal reaction film formation on air baked Fe surfaces that otherwise were highly resistance to reaction film formation. The surface morphology, roughness, and thickness of the thermal reaction films, as measured by atomic force microscopy (AFM), are reported as well as their chemical compositions, as studied with Electron Dispersive X-ray Spectroscopy (EDS). The coefficients of friction measured on the thermal reaction films during dry solid-solid contact are also reported.Lubricants 2018, 6, 56 2 of 14 existing phosphate esters additives, rather than outright replacing them. An appropriate strategy to limit their use levels while also retaining their function is to blend them with a synergistic and environmentally friendly additive. The overarching goal here is to add the synergistic additive without increasing the amount of phosphorus in the system until it is required to do so. This strategy would be completely practical to implement and applicable in various fields, such as aviation, automobiles, manufacturing, defense, etc., that implement a condition-based maintenance schedule [8].Nanomaterials are emerging as environmentally friendly and effective additives for controlling friction and wear in various applications [9]. Several physical mechanisms such as change in friction mode (sliding to rolling), surface polishing/mending, reduction in cohesive forces via layered materials, etc., and chemical mechanisms, including material delivery/transfer for catalysis, tribofilm formation by tribochemical reactions, etc., have been identified as lubrication mechanisms for nanomaterials [10]. However, nanomaterials should also be able to withstand tough environments under EP conditions during boundary lubrication and the high operating temperatures of aircraft engines if they are to be successfully blended with currently used additives. This requires that nanomaterials have, among other properties, a high melting point, high hardness, and favorable chemical reactions to allow rigid bonding onto the surface, together with the anti-wear film produced by the phosphate ester [5].Among the nanomaterials discovered and studied so far, nanodiamonds are the leading candidates from the po...

show abstract

Section: Discussionmentioning

confidence: 99%

Synergistic Effect of Nanodiamond and Phosphate Ester Anti-Wear Additive Blends

et al. 2018

View full text Add to dashboard Cite

show abstract

“…As described previously, the CPL bound-and-mobile film on flat SiO 2 has the windshield wiper effect [4,5]. When the CPL-coated SiO 2 ball rubs against the CPL-coated SiO 2 surface, the CPL multilayer can be wiped away towards the ends of the contact track.…”

Section: Resultsmentioning

confidence: 85%

“…Figure 2a compares the friction data in dry conditions at 2, 16, and 32 s intervals between slide cycles for a flat sample and a sample with 520 nm nanowell texturing. On the flat surface, as the wait interval between cycles increases, the CPL layers provide lubrication for longer cycles as predicted by the windshield wiper effect [4,5]. For the 520 nm nanowell-textured surface, the same thickness lubrication film works for much longer cycles at short wait intervals.…”

Section: Resultsmentioning

confidence: 89%

See 1 more Smart Citation

Effects of Nanoscale Surface Texturing on Self-Healing of Boundary Lubricant Film via Lateral Flow

2011

View full text Add to dashboard Cite

Surface texturing of silicon substrates with nanowells can change the lubricious performance of cationic polymer lubricant (CPL), a bound-and-mobile lubricant consisting of a polydimethylsiloxane (PDMS) backbone with covalently bonded quaternary ammonium iodide cations. The filled nanowell reservoirs enhance selfhealing within the contact track since they can readily provide CPL to near-by regions. However, once this initial reservoir is completely consumed and depleted, the empty nanowells interfere with long-distance lateral flow process since they act as a reservoir that needs to be filled during the flow.

show abstract

“…This raises the question of the possible physical origins of the factor of the approximate doubling in the resistance: A dielectric material (for dodecane, K = 2) confined within the contact is expected to raise the resistance by many orders of magnitude [6,31] and depend closely on the number of molecules confined within. It is possible that the molecules, being physisorbed and mobile, are not actually within the contacts but squeezed out into the regions immediately outside of them [46][47][48][49][50][51]. Indeed, Patton et al [3] reported that contact force of 200 lN is high enough to remove SAM molecules outside of MEMS contacts.…”

Section: Discussionmentioning

confidence: 99%

Electrical Contact Resistance and Device Lifetime Measurements of Au-RuO2-Based RF MEMS Exposed to Hydrocarbons in Vacuum and Nitrogen Environments

et al. 2011

Self Cite

View full text Add to dashboard Cite

Electrical Contact Resistance (ECR) measurements are reported for RF micro-electromechanical switches with Au-RuO 2 contacts, situated within an ultrahigh vacuum system equipped with in situ oxygen plasma cleaning capabilities. Two studies are reported, each involving a comparison of the ECR in vacuum and nitrogen environments for measurements performed immediately after cleaning. The first study reports measurements of initial resistance (resistance measured upon first time closure) versus pressure as dodecane gas is admitted to the chamber. A significant increase is observed at pressures in vacuum as low as 10 -5 torr, (P/P sat \ 10 -4 ) consistent with earlier reports involving repetitive cycling of macroscopic switches in partial pressures of hydrocarbons in nitrogen. Somewhat unexpectedly, however, the resistance only doubles, even for pressures sufficiently high as to result in full monolayer condensation. In a second study, switch lifetimes in vacuum (10 -8 -10 -9 torr) and nitrogen gas environments are compared, for switches operated immediately afterward, or alternatively left open for a number of days before operation. Although it was expected that vacuum would reduce and/or prevent contamination of the electrical contact surfaces, no enhancement or extension of lifetime was observed: Continuous operation of a switch in a nitrogen environment immediately after plasma cleaning was in fact the only procedure observed to indefinitely prolong device lifetime. The results suggest that (1) Hydrocarbon reaction products, but not mobile physisorbed hydrocarbons themselves, are responsible for increasing ECR by orders of magnitude and (2) Repetitive cycling motion of a clean switch in nitrogen inhibits formation of physisorbed hydrocarbon contaminants on the contacts, while vacuum levels far superior to 10 -9 torr are required to prevent contamination.

show abstract

STM, QCM, and the Windshield Wiper Effect: A Joint Theoretical−Experimental Study of Adsorbate Mobility and Lubrication at High Sliding Rates

Cited by 15 publications

References 15 publications

Synergistic Effect of Nanodiamond and Phosphate Ester Anti-Wear Additive Blends

Synergistic Effect of Nanodiamond and Phosphate Ester Anti-Wear Additive Blends

Effects of Nanoscale Surface Texturing on Self-Healing of Boundary Lubricant Film via Lateral Flow

Electrical Contact Resistance and Device Lifetime Measurements of Au-RuO2-Based RF MEMS Exposed to Hydrocarbons in Vacuum and Nitrogen Environments

Contact Info

Product

Resources

About