Is Ultralow Friction on Graphite Sustainable in Contaminated Environments?
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arXiv
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| Autori principali: | , |
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| Natura: | Preprint |
| Pubblicazione: |
2024
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| _version_ | 1866910582246998016 |
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| author | Gao, Hongyu Sukhomlinov, Sergey |
| author_facet | Gao, Hongyu Sukhomlinov, Sergey |
| contents | Structural lubricity arises typically at incommensurate, well-defined dry contacts where short-range elastic instability is significantly mitigated. However, under ambient conditions, airborne molecules adsorb onto solid surfaces, forming an intervening viscous medium that alters interfacial properties. Using molecular dynamics simulations with a newly parameterized interfacial potential, we investigate the preservation of ultralow friction on graphite with physisorbed n-hexadecane (HEX) as a model contaminant. Our findings reveal that a well-ordered monolayer of HEX molecules strongly adheres to the graphite surface, replicating its lattice structure and maintaining solid-like behavior, which leads to orientation-dependent shear stresses-an effect absent on a gold (111) surface. As the contaminant film thickens, this orientation effect diminishes. Additionally, as coverage increases from zero to one monolayer, the shear stress-velocity relationship transitions from Coulomb to quasi-Stokesian and then to quasi-Coulomb, highlighting the role of molecular displacement in high-velocity dissipation. Despite a hundredfold increase in shear stress compared to dry sliding, superlubricity on graphite persists under ambient conditions, enhancing our conventional understanding of structural lubricity. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2408_16677 |
| institution | arXiv |
| publishDate | 2024 |
| record_format | arxiv |
| spellingShingle | Is Ultralow Friction on Graphite Sustainable in Contaminated Environments? Gao, Hongyu Sukhomlinov, Sergey Materials Science Structural lubricity arises typically at incommensurate, well-defined dry contacts where short-range elastic instability is significantly mitigated. However, under ambient conditions, airborne molecules adsorb onto solid surfaces, forming an intervening viscous medium that alters interfacial properties. Using molecular dynamics simulations with a newly parameterized interfacial potential, we investigate the preservation of ultralow friction on graphite with physisorbed n-hexadecane (HEX) as a model contaminant. Our findings reveal that a well-ordered monolayer of HEX molecules strongly adheres to the graphite surface, replicating its lattice structure and maintaining solid-like behavior, which leads to orientation-dependent shear stresses-an effect absent on a gold (111) surface. As the contaminant film thickens, this orientation effect diminishes. Additionally, as coverage increases from zero to one monolayer, the shear stress-velocity relationship transitions from Coulomb to quasi-Stokesian and then to quasi-Coulomb, highlighting the role of molecular displacement in high-velocity dissipation. Despite a hundredfold increase in shear stress compared to dry sliding, superlubricity on graphite persists under ambient conditions, enhancing our conventional understanding of structural lubricity. |
| title | Is Ultralow Friction on Graphite Sustainable in Contaminated Environments? |
| topic | Materials Science |
| url | https://arxiv.org/abs/2408.16677 |