Multifaceted Surface Coatings from Composite Dry Lubrication Schemes

Two-dimensional (2D) materials are an attractive route to modulate interfacial behavior both in dry lubricant applications and in electronics. This positions them particularly well for potential use as multipurposed coatings for emerging technologies such as electric vehicles or space-based interfaces. As stand-alone materials, there is a growing selection of 2D materials with well controlled chemical composition and mechanical and electronic properties. These properties can be further altered through nanoscopic curvatures to control out-of-plane bending. With respect to dry lubrication, composite systems comprised of 2D materials and nanoparticles provide low friction through a nanoscrolling mechanism in which the 2D materials wrap around the nanoparticles. With respect to electronic applications, surfaces with nanoscopic roughness provide a platform to tune the bandgap of 2D materials through induced strain. This project seeks to understand the mechanical-electronic intersection of these observed effects, focusing on induced strain in 2D materials that have scrolled around nanoparticles as a result of sliding forces. Molybdenum disulfide (MoS2) and phosphorene 2D materials were used in conjunction with metal oxide nanoparticles of varying sizes, implemented to induce varying degrees of strain. Sliding tests were carried out at nanoscopic length scales (atomic force microscope, AFM) and macroscope length scales (rheometer tribology adapter). Postsliding confocal Raman analysis assessed the degree of strain through monitoring peak shifts. This helps establish workable parameters for designing tailored multipurposed surface coatings.