In Vacuo Tribological Behavior of Polytetrafluoroethylene (PTFE) and Alumina Nanocomposites: The Importance of Water for Ultralow Wear

Ewin, Jeffrey J.; Krick, Brandon A.

doi:10.1007/s11249-013-0256-1

Cited by 89 publications

(68 citation statements)

References 30 publications

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“…Or perhaps, the wear resistance mechanism does not most importantly involve improved mechanical composite properties, but instead tribochemical reactions within the thin sliding surface and transfer films, as has been suggested for alumina nanoparticle-filled PTFE where the occurrence of extreme wear resistance is observed to be accompanied by formation within the transfer film of water-associated counterface metal/perfluorinated acid reaction products [25], and the substantial loss of this extreme wear resistance upon the removal of reactive water vapor through the use of reduced test chamber pressures \10 -5 Torr [26]. Though the underlying wear resistance mechanism of graphene plateletfilled PTFE remains uncertain at this point, it nonetheless appears to be a novel self-lubricating tribomaterial holding great promise with extreme wear resistances well in excess of many of the PTFE composites commonly available now, especially at reduced platelet thickness.…”

Section: Tensile Behavior Of Graphene-filled Ptfe and Possible Connecmentioning

confidence: 90%

Effect of Platelet Thickness on Wear of Graphene–Polytetrafluoroethylene (PTFE) Composites

2015

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Under conditions of dry sliding against polished stainless steel, the steady-state wear rates of composites of polytetrafluoroethylene (PTFE) filled with graphene platelets with typical platelet thickness varying between 1.25 and 60 nm were measured. The fraction of the graphene platelets was varied between 0.02 and 30 wt%, also including 0 % unfilled PTFE. With 4 % loading of the 1.25 and 1.6 nm thick graphene platelets, the measured steady-state wear rates approached *4 9 10 -7 mm 3 /Nm levels which are roughly three orders of magnitude lower than that measured for unfilled PTFE, decreasing further to 10 -7 mm 3 /Nm at 10 % loading. In addition, among all the tested graphene platelets, the thinnest graphene platelets already imparted considerable wear resistance even at a low 0.32 % loading. The thicker graphene platelets also started providing some slight resistance to sliding wear but not until a greater filler loading of 1.1 %. For a given graphene platelet, there appears to be a lowest achievable steady-state wear rate, while the filler loading is gradually increased. For the 8 nm thick graphene platelets, this minimum was found to be about 3 9 10 -7 mm 3 /Nm at a filler loading of about 20 %. When the wear rates are plotted as a function of the filler loading on log-log axes, for each of the graphene platelets, the wear rates are found to decrease linearly beyond a threshold filler loading up to at least 10 % filler loading. Wear rates corresponding to each type of graphene platelet fall on its own line on such a plot. However, when the wear rates are instead plotted as a function of the filler surface area available per unit mass of the composite, the data (with the exception of the thickest 60 nm platelets) collapse around a master line with slope of about -1.73.

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Section: Tensile Behavior Of Graphene-filled Ptfe and Possible Connecmentioning

confidence: 90%

Effect of Platelet Thickness on Wear of Graphene–Polytetrafluoroethylene (PTFE) Composites

2015

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“…Burris and Sawyer found that wear rates of PTFE and its composites tended to increase with the cube of the measured transfer film thickness over three orders of magnitude of change in wear rate [13]. Pitenis et al found similar trend during in vacuo wear tests of PTFE composites [25]. Blanchet et al [35] proposed that wear is likely related to the transfer film coverage of the wear track.…”

Section: Transfer Film Morphologymentioning

confidence: 97%

“…Unfortunately, the XPS observation provided no direct insight into what the tribochemical species was or why it formed. Krick et al [23] and Pitenis et al [25] both found the removal of environmental moisture caused increased wear rates (from K~10´7 to K~10´5 mm 3 /Nm), reduced transfer film quality, severe counterface abrasion, and loss of transfer film discoloration. The remarkable effects of water removal alone strongly suggested a wear reduction mechanism of tribochemical origins.…”

Section: Chemistry Of the Transfer Filmmentioning

confidence: 99%

“…In addition to producing thinner and more uniform transfer films, low-wear alumina-PTFE transfer films are obviously discolored [13,18,20,[23][24][25][26][27]29,31,32,[37][38][39], which suggests chemical reactions had taken place and possibly enhanced adhesion of the transfer film. In 2013, Ye and Burris used optical microscopy to determine the degree to which transfer films persist during sliding [20].…”

Section: The Effects Of Filler Characteristics On Transfer Films and mentioning

confidence: 99%

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A Review of Transfer Films and Their Role in Ultra-Low-Wear Sliding of Polymers

Burris

Xie

2016

Lubricants

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Abstract:In dry sliding conditions, polytetrafluoroethylene (PTFE) composites can form thin, uniform, and protective transfer films on hard, metallic counterfaces that may play a significant role in friction and wear control. Qualitative characterizations of transfer film morphology, composition, and adhesion to the counterface suggest they are all good predictors of friction and, particularly, wear performance. However, a lack of quantitative transfer film characterization methods and uncertainty regarding specific mechanisms of friction and wear control make definitive conclusions about causal relationships between transfer film and tribological properties difficult. This paper reviews the state of the art in the solid lubricant transfer film literature and highlights recent advances in quantitative characterization thereof.

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“…The solid lubrication materials mainly included polymer, graphite, copper alloy, MoS 2 composite materials, soft metal coatings (Ag, Au, Pb, In) and diamond-like carbon (DLC), and so on [7][8][9][10]. The liquid lubricants applied in aerospace industry were mostly concentrated on multi-alkylated cyclopentanes, perfluoropolyethers and silicone oils [11][12][13].…”

Section: Introductionmentioning

confidence: 99%

Tribological Performance and Lubrication Mechanism of Solid–Liquid Lubricating Materials in High-Vacuum and Irradiation Environments

Liu

Wang

et al. 2015

Tribol Lett

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In this paper, six solid-liquid lubricating materials have been prepared based on two kinds of liquid lubricants including perfluoropolyethers oil (PFPE) and chlorinated-phenyl and methyl-terminated silicone oil (CPSO) and three different solid lubrication materials [polyimide (PI), polytetrafluoroethylene and Cu-based alloy] by the dip-coating method. The tribological behaviors of these lubricating materials were comparatively investigated in high-vacuum condition. The results showed that the polymer-based solid-liquid lubricating materials exhibited the excellent tribological properties, which mainly attributed to the hydrodynamic lubrication. Moreover, as for the same solid substrate, the smaller the value of the steady-state contact angle was, the higher the friction coefficient was. Meanwhile, the effect of atomic oxygen (AO) and proton (H ? ) irradiations on structure and tribological properties of the PI/CPSO and PI/PFPE was further investigated in this work. The experimental results indicated that irradiations induced the degradation of the lubricating oil, which resulted in the increment of the friction coefficient and wear rate, thus decreasing the lubricating performance. In addition, the effect induced by H ? irradiation was more serious than that by AO irradiation. PI/ CPSO solid-liquid lubricating material has good irradiation stability compared with PI/PFPE.

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In Vacuo Tribological Behavior of Polytetrafluoroethylene (PTFE) and Alumina Nanocomposites: The Importance of Water for Ultralow Wear

Cited by 89 publications

References 30 publications

Effect of Platelet Thickness on Wear of Graphene–Polytetrafluoroethylene (PTFE) Composites

Effect of Platelet Thickness on Wear of Graphene–Polytetrafluoroethylene (PTFE) Composites

A Review of Transfer Films and Their Role in Ultra-Low-Wear Sliding of Polymers

Tribological Performance and Lubrication Mechanism of Solid–Liquid Lubricating Materials in High-Vacuum and Irradiation Environments

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