The Effects of Environmental Water and Oxygen on the Temperature-Dependent Friction of Sputtered Molybdenum Disulfide

Khare, H. S.; Burris, David L.

doi:10.1007/s11249-013-0233-8

Cited by 122 publications

(107 citation statements)

References 28 publications

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“…For each sample, the friction and wear increases in the order dry N 2 -dry air-humid N 2 -humid air, which is also in agreement with the results presented by Khare and Burris for pure MoS 2 coatings [26,27]. The same order is found for the onset of high friction for higher N contents.…”

Section: Effect Of Atmospheresupporting

confidence: 91%

Section: Effect Of Atmospheresupporting

confidence: 71%

“…The principle of moisturedriven or water-induced oxidation may be valid, but the current results (as well as those of Khare and Burris for MoS 2 [26,27]) show that the simultaneous presence of H 2 O and O 2 is more severe than only H 2 O. We propose that the combination of increased oxidation to WO 3 and higher sliding friction for WS 2 leads to harsh conditions.…”

Section: Effect Of Atmospherementioning

confidence: 44%

“…For MoS 2 , the presence of H 2 O has been reported to cause a higher shear strength of the otherwise easily sheared planes, thereby increasing the friction [1,26,[28][29][30]. The shear strength increase due to H 2 O is also in agreement with the often observed lowering of friction around 100°C for tests in humid air due to removal of water [26,31,32]. In the present study, coatings with low N content in humid N 2 exhibit μ ≈ 0.1, which should be indicative of the sliding friction for WS 2 in the presence of H 2 O, and is similar to other reports of WS 2 or MoS 2 in humid conditions [2,11,26,31].…”

Section: Effect Of Atmospherementioning

confidence: 99%

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Influence of composition, structure and testing atmosphere on the tribological performance of W–S–N coatings

Sundberg

Nyberg

Särhammar

et al. 2014

Surface and Coatings Technology

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W-S-N coatings deposited by reactive magnetron sputtering offer the possibility of ultra-low friction in unlubricated sliding. In this work, W-S-N coatings of different composition and structure have been deposited, characterised and evaluated with respect to the tribological performance and tribofilm formation. The composition was varied by changing the flow of N 2 into the deposition chamber, leading to N contents ranging from 0 to 47 at.%. W-S-N coatings deposited without substrate heating are amorphous, while substrate heating results in coatings containing nanocrystalline tungsten sulphide (WS x ) for low N contents, and nanocrystalline tungsten nitride (W y N) at a high N content. The coatings were tribologically tested against steel balls in four different atmospheres-dry N 2 , dry air, humid N 2 and humid air-to study the effects of atmospheric O 2 and H 2 O both separately and simultaneously. In dry N 2 , all coatings exhibited an excellent performance with very low friction (μ ≈ 0.02) and wear. Notably, this included the N-richest and hardest coating, containing nanocrystalline W y N and only 13 at.% of S. The friction and wear increased on changing the atmosphere, in the order of dry airhumid N 2 -humid air. In these three non-inert atmospheres, the friction and wear also increased with increasing N content of the coating. It is thus concluded that the presence of O 2 , the presence of H 2 O, and a high N content (i.e., low W and S contents) are three factors increasing the risk of high friction and wear, especially when occurring together. Raman spectroscopy mapping of the contact surfaces on the coatings and the balls showed that low friction and wear is connected to the presence of WS 2 tribofilms in the contact, and that the three previously mentioned factors affect the formation and function of this tribofilm.

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Section: Effect Of Atmospheresupporting

confidence: 91%

Section: Effect Of Atmospheresupporting

confidence: 71%

Section: Effect Of Atmospherementioning

confidence: 44%

Section: Effect Of Atmospherementioning

confidence: 99%

See 2 more Smart Citations

Influence of composition, structure and testing atmosphere on the tribological performance of W–S–N coatings

Sundberg

Nyberg

Särhammar

et al. 2014

Surface and Coatings Technology

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“…Studies of MoS 2 have primarily focused on sputtered coatings in gas or vapor environments, with water and oxygen often being the vapors of interest. These tests often suggest that oxidation impedes lamellar shear to cause high friction, although the temperatures for which oxidation occurs varies [23]. Both experimental and computational studies have been performed to elucidate the atomistic shear conditions, which found frictional anisotropy and oxidation identified as influential phenomena [23][24][25][26][27].…”

Section: Introductionmentioning

confidence: 99%

Origin of Ultra-Low Friction of Boric Acid: Role of Vapor Adsorption

2015

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Boric acid is a lamellar solid lubricant that can give an ultra-low friction coefficient. The origin of this ultra-low friction of boric acid was investigated using tribology and spectroscopy techniques in inert, humid, and organic vapor conditions. It was found that boric acid itself experiences high friction and catastrophic surface wear when rubbed with a stainless steel ball in dry nitrogen or oxygen environments, but it gives very low friction (l = 0.06) in humid and acetone vapor environments. Short-chain alcohol vapors (ethanol and n-pentanol) did not show these ultra-low friction values. Vibrational spectroscopy indicates that the lubricating vapors do not adsorb on the basal plane of the boric acid crystal but likely adsorb onto the edge sites of the lamella. The alcohol molecules impinging from the gas phase readily react with the boric acid to form a high vapor pressure molecule that desorbs from the surface. The ''unlocking'' of the highenergy edge sites by adsorbed acetone and water vapor appears to be needed for the lamella to shear along the basal plane direction.

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Friction Characteristics of Molybdenum Disulfide Thin Films Synthesized via Plasma Sulfurization

et al. 2021

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Herein, the tribological behavior of layered few nanometer‐thick MoS2 thin films is evaluated to identify their applicability to an oil‐free solid‐lubrication coating layer. The MoS2 thin films are synthesized using a plasma sulfurization process with optimized steps and conditions derived from a previous study. MoS2 thin films with different thicknesses are heat treated at 400 °C to investigate the effect on their tribological properties. The ball‐on‐disk method is used to observe the friction and wear behavior of the MoS2 thin films, and this test is carried out under an applied load of 0.5 N in an ambient atmosphere (≈23 °C). The coefficient of friction of the unheated MoS2 layers increases rapidly at 32–36 cycles regardless of the thickness. However, the heat‐treated MoS2 films maintain a lower coefficient of friction for more cycles (60–86 cycles). The heat treatment effect effectively increases the wear life of the MoS2 thin film. Based on this result, it is believed that the heat‐treated MoS2 thin films can be potential solid lubricant candidate for micro‐ and nanoelectromechanical systems.

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The Effects of Environmental Water and Oxygen on the Temperature-Dependent Friction of Sputtered Molybdenum Disulfide

Cited by 122 publications

References 28 publications

Influence of composition, structure and testing atmosphere on the tribological performance of W–S–N coatings

Influence of composition, structure and testing atmosphere on the tribological performance of W–S–N coatings

Origin of Ultra-Low Friction of Boric Acid: Role of Vapor Adsorption

Friction Characteristics of Molybdenum Disulfide Thin Films Synthesized via Plasma Sulfurization

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