Enhanced tribological performance of a supramolecular gel with F-doped carbon dots via in situ directional ultrasonication

Carbon dots (CDs) have attracted considerable attention in tribology due to their nanoscale dimensions and distinct chemical reactivity. However, their tendency to aggregate and sediment in base oils hampers their efficacy as lubricant additives. This study presents a novel approach where F-doped CDs (F-CDs) act as gelling agents under directional ultrasonication. These F-CDs assemble with Span 80 in polyalphaolefin (PAO) to form a supramolecular gel (Gel@F-CDs), and also act as a reinforcing phase to strengthen the structure of the gel. This approach effectively prevents CDs agglomeration in the base oils. We systematically investigate the influence of ultrasonication duration and F-CDs concentration on the morphology, mechanical properties, and tribological behavior of the Gel@F-CDs. Rheological analysis reveals that the Gel@F-CDs possesses a phase transition temperature up to 120 °C and exceptional mechanical properties. Furthermore, the Gel@F-CDs demonstrates superior creep recovery characteristics, significantly reducing friction and wear. This results in a substantial decrease in the coefficient of friction (COF) of PAO from 0.445 to 0.099, and a 47.2% reduction in the wear volume. This strategy is also effective in other base oils like poly(ethylene glycol) (PEG), highlighting its versatility and potential for sustainable development.