Atomic-Scale Friction of Black and Violet Phosphorus Crystals: Implications for Phosphorus-Based Devices and Lubricants

Abstract

Black phosphorus (BP) has received much attention as a two-dimensional layered solid lubricant in reducing friction and protecting against wear. Violet phosphorus (VP) is another stable allotrope of phosphorus with unique layered structures. However, the friction properties of VP have not been explored. Herein, we present a comprehensive study of the atomic-scale friction of BP and VP by friction force microscopy. The friction properties of VP were characterized for the first time. Atomic-scale stick−slip friction measurements along the lattice orientations of BP and VP clearly revealed the correlation between friction anisotropy and crystallographic structures. Relative to the nitrogen atmosphere, the friction behavior of BP and VP in water was also investigated. It was found that the friction coefficient was significantly increased in water, indicating that water was not a good medium for phosphorus achieving superlubricity. The results in this study not only provide indepth insights into the fundamental friction properties of phosphorus but also pave the crucial pathways toward such applications as lubricants in micro/nanoelectromechanical systems and a phosphorus-based superlubric generator with high efficiency and ultralong life.

Nanotribology of Hydrogenated Amorphous Silicon: Sliding-Dependent Friction and Implications for Nanoelectromechanical Systems

“…In the same way, their impacts are of great relevance globally . Due to the number of possible contributions, a myriad of combinations may play diverse roles, with a wide range of open questions, especially when the issues are explored at the nanoscale. , Physicochemical , and structural properties of the body, the counter body, and the medium , where sliding occurs, for example, strongly influence the interactions . With the development of experimental tools , and computational simulations , (including very recent approaches, such as artificial intelligence and machine learning), it is now possible to isolate most of the contributions and deeply understand what may rule and control nanofriction .…”

Liquid-Phase Friction of Two-Dimensional Molybdenum Disulfide at the Atomic Scale

“…Friction is ubiquitous in our everyday activities and is responsible for large amounts of energy dissipation in industrial societies. , Traditional methods to reduce frictional loss involve the use of liquid lubricants between two moving surfaces. However, they are usually not adequate under extreme circumstances like elevated temperature and high pressure, especially in micro- and nano-electromechanical systems. , Two-dimensional (2D) layered materials such as graphene and molybdenum disulfide (MoS 2 ) are of great interest in this context as they typically have low friction and are often used as (additives to) lubricants or low-friction coatings. − In recent years, it has been demonstrated that 2D materials possess unique friction properties even with only a few atomic layers . For instance, the friction on the 2D material surface depends on their layer thickness, where thinner samples have a higher friction force. − At the nanoscale, 2D materials exhibit anisotropic friction with a periodicity of a certain angle, such as 60° and 180°. − In addition, the friction behavior on 2D materials shows a dependency on sliding history, where the friction force during loading is smaller than that during unloading at a given load. ,, However, most of the studies mentioned above were carried out either under ultra-high vacuum conditions or in a gas-phase environment.…”

Dissipation Mechanisms and Superlubricity in Solid Lubrication by Wet-Transferred Solution-Processed Graphene Flakes: Implications for Micro Electromechanical Devices

“…A central theme of the current tribology research concerns the investigation of novel classes of two-dimensional nanomaterials, that might effectively promote ultralow sliding friction regimes in real-world applications, thanks to their unique physical properties, improved quality, greater flexibility, or low-cost scalable production routes. − In this respect, solution-processed single-layer/few-layer graphene (SLG/FLG) flakes, supplied to macroscale rotating, and sliding contacts via liquid dispersions are gaining increasing attention as friction modifiers in practical applications. − Compared to mechanically cleaved or grown graphene, liquid dispersions appear more suitable for low-cost mass production. They do not require time-consuming optimization to coat different material substrates and are virtually able to conformally coat interfaces of arbitrary geometry.…”