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" Tribological Study of Ultrathin 2d-Materials Against Application Oriented Counter-Surfaces Under Controlled Environment "
Arif, Taib Muhammad
Filleter, Tobin
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Latin Dissertation
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English
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| Record Number
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1108581
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| Doc. No
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TLpq2466749587
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| Main Entry
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Arif, Taib Muhammad
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Filleter, Tobin
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| Title & Author
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Tribological Study of Ultrathin 2d-Materials Against Application Oriented Counter-Surfaces Under Controlled Environment\ Arif, Taib MuhammadFilleter, Tobin
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| College
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University of Toronto (Canada)
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| Date
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2020
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| student score
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2020
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| Degree
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Ph.D.
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| Page No
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181
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| Abstract
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Nanoscale tribological behavior of ultrathin 2D-materials (i.e. graphene, MoS2, and their oxidized structures) were investigated at varying humidity using application motivated counter-surfaces (SiO2, 440C-steel, oxidized-titanium, and oxidized-copper). By varying the humidity, water dependent mechanisms were identified. Significant water was observed to intercalate within graphene oxide (GO) and was identified to initiate wear once the functional groups were passivated. GO exhibited higher friction compared to ultrathin-graphene, with a more sensitive response to humidity. The less desirable tribological behavior on GO and the detrimental influence of water were attributed to the presence of functional groups. Ultrathin-MoS2 and ultrathin-graphene exhibited increasing friction and adhesion trends with humidity against SiO2 counter-surfaces. For both the materials, interfacial water adsorption dominated the tribological behavior. However, friction and adhesion on ultrathin-MoS2 increased at lower humidity and was attributed to stronger physical MoS2-water interaction. Friction on oxidized-MoS2 was found to be significantly higher and exhibited greater sensitivity to water as compared to ultrathin-MoS2. The presence of oxygen along the basal plane of ultrathin-MoS2 creates a non-uniform interfacial charge distribution resulting in higher resistance experienced by the sliding counter-surface. Comparison between ultrathin-MoS2 and oxidized-MoS2 confirms that oxygen alone increases friction and when coupled with the presence of water, both effects are additive. Against a 440C-steel counter-surface, ultrathin-graphene exhibited lower friction, interfacial-shear-strength, and adhesion than ultrathin-MoS2. This behavior was attributed to the stronger chemical interaction between 440C-steel/MoS2 as compared to the weaker physical interaction between steel/graphene. Furthermore, ultrathin-graphene and ultrathin-MoS2 exhibit contrary behavior to water, where water was seen to increase friction on ultrathin-graphene yet reduced friction on ultrathin-MoS2. The reduction in friction due to water adsorption was attributed to the suppression of the strong interfacial interaction by acting as a temporary protective film between the 440C-steel/MoS2 interface. Lastly, both oxidized-titanium and oxidized-copper counter-surfaces were found to interact chemically with ultrathin-MoS2 and ultrathin-graphene. Friction and adhesion on ultrathin-MoS2 were lower against both the counter-surfaces as compared to ultrathin-MoS2. It was identified that the charge distribution and energy variation along the interface dominated the tribological behavior. Interfaces with localized charge build-up and higher energy variation resulted in higher friction and adhesion.
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Lubricants lubrication
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Materials science
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Mechanical engineering
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Tribology
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