Effect of Humidity and Water Intercalation on the Tribological Behavior of Graphene and Graphene Oxide

Abstract

In this work, the effect of humidity and water intercalation on the friction and wear behavior of few-layers of graphene and graphene oxide (GO) was studied using friction force microscopy. Thickness measurements demonstrated significant water intercalation within GO affecting its surface topography (roughness and protrusions), whereas negligible water intercalation of graphene was observed. It was found that water intercalation in GO contributed to wearing of layers at a relative humidity as low as ∼30%. The influence of surface wettability and water adsorption was also studied by comparing the sliding behavior of SiO/GO, SiO/Graphene, and SiO/SiO interfaces. Friction for the SiO/GO interface increased with relative humidity due to water intercalation and condensation of water. In contrast, it was observed that adsorption of water molecules lubricated the SiOSiO interface due to easy shearing of water on the hydrophobic surface, particularly once the adsorbed water layers had transitioned from "ice-like water" to "liquid-like water" structures. Lastly, an opposite friction trend was observed for the graphene/SiO interface with water molecules failing to lubricate the interface as compared to the dry graphene/SiO contact.

Understanding the Independent and Interdependent Role of Water and Oxidation on the Tribology of Ultrathin Molybdenum Disulfide (MoS2)

“…[11] While there is some understanding of mechanisms (localized interlayer shearing, puckering effect, electron phonon coupling etc.) at the nanoscale associated with water influencing friction for graphene, graphene oxide (GO) and graphite edges [15][16][17][18][19][20][21][22][23][24] , there is only limited understanding for MoS2 and oxidized-MoS2 at the nano/molecular scale. Advancement of technological tools such as the atomic force microscope (AFM)…”

“…has allowed studying the fundamental mechanisms governing friction at atomic/molecular scale. [17,18,25,26] In particular, recent advancements for controlling the environment locally around the single AFM contact have expanded our understanding, by moving away from studying friction as a function of normal load only to consider the role of other variables such as relative humidity [15] and temperature. [27,28] At the atomic scale, MoS2 is categorized as a 2D transition metal dichalcogenide (TMD), consisting of a covalently bonded tri-layer structure, with molybdenum atoms sandwiched between sulfur atoms.…”

“…[39] While wettability has been shown to influence the friction behavior on other 2D materials, it has not been studied for 2D-MoS2. [15] Therefore, there is a need for studying the influence of water and oxidation on MoS2 to better understand how they can improve or degrade frictional behavior, while also conducting complementary atomistic simulations for further insights on the mechanisms. Such fundamental understanding will be of great importance in particular for space applications where MoS2 coating already undergo extensive testing ensuring its durability.…”

A Dynamic 3D Hydrogen‐Bonded Organic Frameworks with Highly Water Affinity

“…At this point, the related adsorbent materials should possess a high affinity to H 2 O with low energy costs associated with the activation, regeneration, and recycling. Much efforts then have been devoted to the design and preparation of such materials . Zeolites 3A, 4A, 5A, 13X, silica gel, and activated alumina are the well‐known dehydrating agents for the aforementioned purpose.…”

“…Zeolites 3A, 4A, 5A, 13X, silica gel, and activated alumina are the well‐known dehydrating agents for the aforementioned purpose. However, none of them belongs to the ideal candidate due to a relatively low uptake amount or energy‐intensive regeneration steps . More recently, Cadiau et al have demonstrated that the fluorinated MOFs NiAlF 5 (H 2 O) (pyrazine) 2 ·2(H 2 O) and NiFeF 5 (H 2 O)(pyrazine) 2 ·4(H 2 O) can selectively remove water vapor from industrial gas streams with moderate energy input for regeneration, thus emerging as one of strong competitors for commonly used desiccants.…”