Surface Structure of Hydrogenated Diamond-like Carbon: Origin of Run-In Behavior Prior to Superlubricious Interfacial Shear
- 27 January 2015
- journal article
- Published by American Chemical Society (ACS) in Langmuir
- Vol. 31 (5), 1711-1721
- https://doi.org/10.1021/la504612c
Abstract
The oxidized layers at the surface of hydrogenated diamond-like carbon (H-DLC) were studied with X-ray photoelectron spectroscopy, near-edge X-ray absorption fine structure, and Raman spectroscopy. The structure of these layers was correlated with the friction and wear behavior observed on H-DLC. H-DLC is well-known for its ultralow friction in inert environments, but the steady superlubricious state is always preceded by a run-in period with a high friction. It was hypothesized that the run-in period is related to the surface oxide layer formed naturally upon exposure of the sample to air. To test this hypothesis, thermal oxide layers were grown, and their structures were analyzed and compared with the native oxide layer on a pristine sample. It was found that the Raman spectra of the surface oxide layers of H-DLC have higher D/G band ratio than the bulk, indicating a larger amount of aromatic clusters compared to the bulk film. Thick oxide layers grown at 300 °C showed a run-in friction behavior that resembled the friction of graphite. The run-in periods were found to become longer when the thickness of the oxide layers increased, indicating that the run-in behavior of H-DLC is attributed to the removal of the surface oxide layers.Keywords
Funding Information
- National Science Foundation (ECS-0335765)
- Division of Civil, Mechanical and Manufacturing Innovation (CMMI-1131128)
- Basic Energy Sciences (DE-AC02-06CH11357)
- Materials Research Institute,, Pennsylvania State University (ECS-0335765)
This publication has 58 references indexed in Scilit:
- Understanding Run-In Behavior of Diamond-Like Carbon Friction and Preventing Diamond-Like Carbon Wear in Humid AirLangmuir, 2011
- Atomistic Factors Governing Adhesion between Diamond, Amorphous Carbon and Model Diamond Nanocomposite SurfacesJournal of Adhesion Science and Technology, 2010
- On the hydrogen lubrication mechanism(s) of DLC films: An imaging TOF-SIMS studySurface and Coatings Technology, 2008
- Run-in behavior of nanocrystalline diamond coatings studied by in situ tribometryWear, 2008
- Origin of Ultralow Friction and Wear in Ultrananocrystalline DiamondPhysical Review Letters, 2008
- Investigation of Initial and Steady-State Sliding Behavior of a Nearly Frictionless Carbon Film by Imaging 2- and 3-D TOF-SIMSTribology Letters, 2007
- Environmental effects on the friction of hydrogenated DLC filmsTribology Letters, 2006
- Modeling the Tribochemical Aspects of Friction and Gradual Wear of DLC FilmsPublished by Springer Science and Business Media LLC ,2006
- How to restore superlow friction of DLC: the healing effect of hydrogen gasTribology International, 2004
- Superlow friction behavior of diamond-like carbon coatings: Time and speed effectsApplied Physics Letters, 2001