Lanzhou Institute of Chemical Technology has made progress

[ Instrument network and instrument research and development ] "Super-lubrication" is an important scientific discovery in modern tribological research. It originated from the theoretical prediction of "Structural Super-Lubrication" put forward around 1990: When two ideal, flat, rigid crystal planes are in incommensurate contact When relative movement occurs in the method, the atomic potential effects between the upper and lower surfaces cancel each other, the slip barrier is zero, and the friction disappears or approaches zero. The engineering realization of the "structural super-lubrication" theory is expected to bring revolutionary progress for energy saving and consumption reduction, and mechanical equipment design. Through years of research, it is currently possible to achieve nano- and micro-contact scale "structural super-lubrication" on the surface of some ideal layered crystalline materials (such as highly oriented graphite), but at the macro-engineering contact scale, there are disorder, adsorption and defects on the surface of the material Etc., how to achieve super-lubrication at the macro contact scale has become the focus of research and the bottleneck of engineering applications.

Recently, the Research Group of Wear and Surface Engineering of Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences put forward a new method for macro-scale realization of "structural super-lubrication" table/interface design, which can achieve robust super-lubrication performance under the condition of engineering substrate surface and macroscopic contact. "Structural ultra-lubrication" is moving from micro-nano scale to macro-engineering scale, which is of great significance to the realization of engineering application of the new concept technology of ultra-lubrication.

The research work is based on two core design ideas: based on the consideration that the micro-nano contact size is easier to meet the ideal conditions for obtaining structural super-lubrication, the micro-nano bumps are actively constructed on the rough surface of the substrate through laser etching and other surface treatment technologies, and the macro The surface contact is decomposed into countless micro-nano point contacts; a special heterogeneous two-dimensional nano-structured lubricating layer is designed and prepared on the surface, through the layer-layer contact slip mode, weak chemical interaction between the layers, and incommensurable crystals. The control of grid matching obtains the super-lubrication state at each contact point. A large number of contact points are combined to form a macroscopic super-lubrication on the entire contact surface. The ball-disk friction tester was used for evaluation. Under the contact stress of 0.5 GPa, the rough steel-steel contact friction pair obtained stable and long-lasting super-lubrication performance (friction coefficient 0.007, life greater than 1×106 revolutions) . Further, a bonded lubricating coating is prepared through a composite adhesive, which still maintains super-lubricating properties under high contact stress (1.3 GPa), showing excellent engineering practical value.

Studies have found that when covalent/ionic heterogeneous two-dimensional laminates are combined, they exhibit a synergistic lubricating effect. Covalent compounds (such as graphene) form bonds by sharing electron pairs, and have orientation and saturation. During the sliding process, the dangling bonds at adjacent layer defects will have a strong chemical effect. However, ionic compounds (such as molybdenum disulfide) rely on the attraction between positive and negative ions, which do not have orientation and saturation. Even if the loss of local defect ions occurs, the surrounding ions will be supplemented to shield and weaken their interaction with the outside. . The covalent/ion laminated composite design can effectively block the strong chemical interaction between adjacent layers of covalent compounds, and weaken the adverse effects of defects and edge bonds in the macroscopic friction process. Heterogeneous lattice matching also exhibits natural incommensurability in the process of macroscopic friction, and can achieve super-lubrication without relying on the slip angle. This theoretical understanding can explain the synergistic lubrication mechanism of traditional graphite and molybdenum disulfide composite materials.

Related research results were published online on Advanced Materials. PhD student Li Panpan is the first author of the paper, and Geely (a member of the Youth Innovation Promotion Association of the Chinese Academy of Sciences), Li Hongxuan and Chen Jianmin are the co-corresponding authors. The research work is funded by the National Natural Science Foundation of China, the Joint Aerospace Fund and the Chinese Academy of Sciences Youth Promotion Association.