Towards the use of diamond-like carbon solid lubricant coatings in vacuum and space environments

Fontaine, Julien

doi:10.1243/13506501jet323

Cited by 54 publications

(36 citation statements)

References 62 publications

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“…Since the friction depends on the true contact area, a significantly higher contact area will mean higher friction and more intimate contact leading to the opportunity for bonds to form across the interface, as discussed for hydrogenated carbon films. 51 A detailed analysis of the roughness would be required to further explore how different the contact areas are for UNCD and ta-C samples, both initially and as they wear.…”

Section: B Role Of Carbon Rehybridizationmentioning

confidence: 99%

Influence of surface passivation on the friction and wear behavior of ultrananocrystalline diamond and tetrahedral amorphous carbon thin films

et al. 2012

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Highly sp3 -bonded, nearly hydrogen-free carbon-based materials can exhibit extremely low friction and wear in the absence of any liquid lubricant, but this physical behavior is limited by the vapor environment. The effect of water vapor on friction and wear are examined as a function of applied normal force for two such materials in thin film form -one that is fully amorphous in structure (tetrahedral amorphous carbon, or ta-C) and one that is polycrystalline with <10 nm grains (ultrananocrystalline diamond, or UNCD). Tribologically-induced changes in the chemistry and carbon bond hybridization at the surface are correlated with the effect of the sliding environment and loading conditions through ex-situ, spatially resolved near-edge x-ray absorption fine structure (NEXAFS) spectroscopy. At sufficiently high relative humidity (RH) levels and/or sufficiently low loads, both films quickly achieve a low steady-state friction coefficient and subsequently exhibit low wear. For both films, the number of cycles necessary to reach the steady-state is progressively reduced for increasing RH levels. Worn regions formed at lower RH and higher loads have a higher concentration of chemisorbed oxygen than those formed at higher RH, with the oxygen singly-bonded as hydroxyl groups (C-OH). While some carbon rehybridization from sp 3 to disordered sp 2 bonding is observed, no crystalline graphite formation is observed for either film. Rather, the primary solid-lubrication mechanism is the 2 passivation of dangling bonds by OH and H from the dissociation of vapor-phase H 2 O. This vapor-phase lubrication mechanism is highly effective, producing friction coefficients as low as 0.078 for ta-C and 0.008 for UNCD, and wear rates requiring thousands of sliding passes to produce a few nanometers of wear.

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Section: B Role Of Carbon Rehybridizationmentioning

confidence: 99%

Influence of surface passivation on the friction and wear behavior of ultrananocrystalline diamond and tetrahedral amorphous carbon thin films

et al. 2012

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“…This includes coatings for high-performance tools 4 , hard-disks 5,6 , microelectromechanical systems (MEMS) 7 , automotive and aerospace components 8,9 , and atomic force microscope probes 10 .…”

Section: Introductionmentioning

confidence: 99%

Quantitative Evaluation of the Carbon Hybridization State by Near Edge X-ray Absorption Fine Structure Spectroscopy

2016

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The characterization of the local bonding configuration of carbon in carbon-based materials is of paramount importance since the properties of such materials strongly depend on the distribution of carbon hybridization states, the local ordering, and the degree of hydrogenation. Carbon 1s near edge X-ray absorption fine structure (NEXAFS) spectroscopy is one of the most powerful techniques for gaining insights into the bonding configuration of near-surface carbon atoms. The common methodology for quantitatively evaluating the carbon hybridization state using C1s NEXAFS measurements, which is based on the analysis of the sample of interest and of a highly ordered pyrolytic graphite (HOPG) reference sample, was reviewed and critically assessed, noting that inconsistencies are found in the literature in applying this method. A theoretical rationale for the specific experimental conditions to be used for the acquisition of HOPG reference spectra is presented together with the potential sources of uncertainty and errors in the correctly computed fraction of sp 2 -bonded carbon. This provides a specific method for analyzing the distribution of carbon hybridization state using NEXAFS spectroscopy. As an illustrative example, a hydrogenated amorphous carbon film was analyzed using this method, and showed good agreement with X-ray photoelectron spectroscopy (which is surface sensitive).Furthermore, the results were consistent with analysis from Raman spectroscopy (which is not surface sensitive), indicating the absence of a structurally different near-surface region in this particular thin film material. The present work can assist surface scientists in the analysis of NEXAFS spectra for the accurate characterization of the structure of carbon-based materials.3

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“…Furthermore, the composition of the DLC film strongly affects its tribological properties. For example, the friction coefficient increases with increasing relative humidity (RH) for a-C:H film in ambient air [31], whereas it decreases with increasing RH for a-C or ta-C films [32], and friction coefficients of < 0.01 and as low as 0.001 can be obtained only for a-C:H films under vacuum or inert environment [33][34][35]. These results confirm that hydrogen is key to the low friction behavior of these films and that the presence of water molecules has an adverse effect on their friction behavior [36,37].…”

Section: Diamond-like Carbon Filmsmentioning

confidence: 99%

Carbon-based solid-liquid lubricating coatings for space applications-A review

2015

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Despite continuous improvements in machine elements over the past few decades, lubrication issues have impeded human exploration of the universe because single solid or liquid lubrication systems have been unable to satisfy the ever-increasing performance requirements of space tribology. In this study, we present an overview of the development of carbon-based films as protective coatings, with reference to their high hardness, low friction, and chemical inertness, and with a particular focus on diamond-like carbon (DLC) films. We also discuss the design of carbon-based solid-liquid synergy lubricating coatings with regards to their physicochemical properties and tribological performance. Solid-liquid composite coatings are fabricated via spinning liquid lubricants on solid lubricating films. Such duplex lubricating coatings are considered the most ideal lubrication choice for moving mechanical systems in space as they can overcome the drawback of adhesion and cold-welding associated with solid films under harsh space conditions and can minimize the crosslinking or chain scission of liquid lubricants under space irradiation. State of the art carbon-based solid-liquid synergy lubricating systems therefore holds great promise for space applications due to solid/liquid synergies resulting in superior qualities including excellent friction reduction and anti-wear properties as well as strong anti-irradiation capacities, thereby meeting the requirements of high reliability, high precision, high efficiency, and long lifetime for space drive mechanisms.

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Towards the use of diamond-like carbon solid lubricant coatings in vacuum and space environments

Cited by 54 publications

References 62 publications

Influence of surface passivation on the friction and wear behavior of ultrananocrystalline diamond and tetrahedral amorphous carbon thin films

Influence of surface passivation on the friction and wear behavior of ultrananocrystalline diamond and tetrahedral amorphous carbon thin films

Quantitative Evaluation of the Carbon Hybridization State by Near Edge X-ray Absorption Fine Structure Spectroscopy

Carbon-based solid-liquid lubricating coatings for space applications-A review

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