Friction Reduction and Antiwear Mechanisms of Cerium Sulfide Nanosheets under Different Sliding Conditions

With the rapid development of modern industry, traditional lubricants often require a variety of additives to be used in conjunction with each other, which not only increases the cost but also causes a waste of resources. Therefore, the development of a lubricant additive with both a dyeing function and an antiwear and friction reduction performance can more effectively meet the industrial needs. Cerium sulfide (Ce₂S₃), with its excellent photostability, weather resistance, thermal stability, and nontoxicity, shows great potential as an environmentally friendly pigment. However, traditional methods for synthesizing Ce₂S₃ are typically hindered by high-temperature requirements and potential toxicity issues, which limits the broad application of Ce₂S₃ in lubricants. To overcome these limitations, this study employed a liquid-phase method under mild conditions to synthesize oleylamine-modified, wrinkle-free Ce₂S₃ nanosheets (OA-Ce₂S₃ NSs). The antiwear and friction-reducing properties of OA-Ce₂S₃ NSs in poly alpha-olefin-6 base oils were evaluated under various friction conditions with a four-ball tribometer. Experimental results indicate that OA-Ce₂S₃ NSs significantly enhance the friction-reducing and antiwear performance of lubricants by forming a physical adsorption film and an ultra thick tribochemical reaction film (with a typical thickness of 350 nm and a maximum thickness of up to 700 nm) on the friction surface. Furthermore, the study elucidates the lubrication mechanism of OA-Ce₂S₃ NSs and proposes their sliding mechanism on friction surfaces. This research highlights the potential of Ce₂S₃ nanosheets as lubricant additives and provides future directions for optimizing their synthesis and multifunctional applications, offering new insights into the field of lubrication science.