On the lubricity of transition metal dichalcogenides: an ab initio study

Irving, Benjamin J.; Nicolini, Paolo; Polcar, Tomáš

doi:10.1039/c7nr00925a

Cited by 41 publications

(26 citation statements)

References 71 publications

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“…The sliding energy barrier height for 2H‐MM is 1–2 eV nm −2 , two orders of magnitude larger than those for t‐MM and GM (0.01–0.02 eV nm −2 ), consistent with the Frenkel–Kontorova model, which describes the origin of reduced interlayer friction in 2D multilayers at heterointerfaces and twisted interfaces. [ 17,34,35,41,42 ] These plots also show that the interlayer friction is strongly dependent on the sliding direction and crystallographic bending direction for aligned bilayer MoS 2 , [ 42,43 ] but not for twisted interfaces and heterointerfaces. We obtain similar results for the 1T phase of MoS 2 (see Figure S19, Supporting Information).…”

Section: Resultsmentioning

confidence: 92%

Designing the Bending Stiffness of 2D Material Heterostructures

Han

Hossain

et al. 2021

Advanced Materials

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2D monolayers represent some of the most deformable inorganic materials, with bending stiffnesses approaching those of lipid bilayers. Achieving 2D heterostructures with similar properties would enable a new class of deformable devices orders of magnitude softer than conventional thin‐film electronics. Here, by systematically introducing low‐friction twisted or heterointerfaces, interfacial engineering is leveraged to tailor the bending stiffness of 2D heterostructures over several hundred percent. A bending model is developed and experimentally validated to predict and design the deformability of 2D heterostructures and how it evolves with the composition of the stack, the atomic arrangements at the interfaces, and the geometry of the structure. Notably, when each atomic layer is separated by heterointerfaces, the total bending stiffness reaches a theoretical minimum, equal to the sum of the constituent layers regardless of scale of deformation—lending the extreme deformability of 2D monolayers to device‐compatible multilayers.

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Section: Resultsmentioning

confidence: 92%

Designing the Bending Stiffness of 2D Material Heterostructures

Han

Hossain

et al. 2021

Advanced Materials

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“…This trend contrasts with the predictions of DFT calculations and machine learning models for these materials. [24][25][26] However, those calculations were for sliding between two TMD layers, as opposed to a tip sliding on a TMD sample as in our experiments and simulations. Therefore, the mechanisms proposed by previous calculations for intrinsic interlayer sliding of these materials do not necessarily apply to our case.…”

Section: Resultsmentioning

confidence: 97%

“…24,25 However, if the TMD layers were rotated relative to each other, the resultant incommensurability greatly reduced the energy barrier to sliding. 25 An increase of the energy barrier to sliding with increasing chalcogen size was also predicted using machine learning techniques for Mo-and W-based TMDs. 26 There has been no experimental validation of these predictions so far.…”

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confidence: 99%

Nanoscale Friction Behavior of Transition-Metal Dichalcogenides: Role of the Chalcogenide

et al. 2020

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Despite extensive research on the tribological properties of MoS2, the frictional characteristics of other members of the transition metal dichalcogenide (TMD) family have remained relatively unexplored. To understand the effect of the chalcogen on the tribological behavior of these materials and gain broader general insights into factors controlling friction at the nanoscale, we compared the friction force behavior for a nanoscale single asperity sliding on MoS2, MoSe2, and MoTe2 in both bulk and monolayer forms through a combination of atomic force microscopy (AFM) experiments and molecular dynamics (MD) simulations. Experiments and simulations showed that, under otherwise identical conditions, MoS2 has the highest friction among these materials and MoTe2 the lowest. Simulations complemented by theoretical analysis based on the Prandtl-Tomlinson model revealed that the observed friction contrast between theTMDs was attributable to their lattice constants, which differed depending on the chalcogen. While the corrugation amplitudes of the energy landscapes are similar for all three materials, larger lattice constants permit the tip to slide more easily across correspondingly wider saddle points in the potential energy landscape. These results emphasize the critical role of the lattice constant, which can be the determining factor for frictional behavior at the nanoscale.

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“…4 Ab initio calculations have recently explored the frictional properties of TMDs as a function of chemical composition and bilayer orientation for showing the relationship between incommensurate crystals and superlubricity. 6 Initially, TMDs were applied to sliding components as burnished or sputtered coatings and their application was limited to the context of space lubrication due to their poor performance in humid air. 7 However, after the pioneering synthesis of TMDs as inorganic fullerene nanoparticles, 8,9 their application as a potential lubricant additive was soon envi-saged.…”

Section: Introductionmentioning

confidence: 99%

In situ tribochemical sulfurization of molybdenum oxide nanotubes

et al. 2018

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MoS nanoparticles are typically obtained by high temperature sulfurization of organic and inorganic precursors under a S rich atmosphere and have excellent friction reduction properties. We present a novel approach for making the sulfurization unnecessary for MoO nanotubes during the synthesis process for friction and wear reduction applications while simultaneously achieving a superb tribological performance. To this end, we report the first in situ sulfurization of MoO nanotubes during sliding contact in the presence of sulfur-containing lubricant additives. The sulfurization leads to the tribo-chemical formation of a MoS-rich low-friction tribofilm as verified using Raman spectroscopy and can be achieved both during sliding contact and under extreme pressure conditions. Under sliding contact conditions, MoO nanotubes in synergy with sulfurized olefin polysulfide and pre-formed zinc dialkyl dithiophosphate tribofilms achieve an excellent friction performance. Under these conditions, the tribochemical sulfurization of MoO nanotubes leads to a similar coefficient of friction to the one obtained using a model nanolubricant containing MoS nanotubes. Under extreme pressure conditions, the in situ sulfurization of MoO nanotubes using sulfurized olefin polysulfide results in a superb load carrying capacity capable of outperforming MoS nanotubes. The reason is that while MoO nanotubes are able to continuously sulfurize during sliding contact conditions, MoS nanotubes progressively degrade by oxidation thus losing lubricity.

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On the lubricity of transition metal dichalcogenides: an ab initio study

Cited by 41 publications

References 71 publications

Designing the Bending Stiffness of 2D Material Heterostructures

Designing the Bending Stiffness of 2D Material Heterostructures

Nanoscale Friction Behavior of Transition-Metal Dichalcogenides: Role of the Chalcogenide

In situ tribochemical sulfurization of molybdenum oxide nanotubes

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