Remarkably boosting the lubricity of polyalphaolefin by loading amphiphilic carbon dots stabilized by Span-80

The amphiphilic carbon dots (A-CDs) derived from Tween-80 were used as the lubricant additives of polyalphaolefin (PAO4) with the aid of Span-80. The Span-80 (5.0 wt%) endowed A-CDs with super dispersibility in PAO4 by the hydrogen bond interactions between the hydrophilic head groups of Span-80 and the oxygen-containing groups on A-CDs. At the load of 50 N, the biggest friction and wear reductions for PAO4 triggered by the A-CDs (1.3 wt%) stabilized by Span-80 (5.0 wt%) were 45.4 and 69.8%, respectively. The distinguished tribological performance of A-CDs stabilized by Span-80 illustrated the co-lubrication effect of Span-80 and A-CDs. The wear scar surface analysis results revealed that the A-CDs stabilized by Span-80 distinctly alleviated the adhesive and abrasive wear of friction pair. The favorable smoothness and high O content on wear scar surface lubricated by A-CDs suspension reflected the A-CDs stabilized by Span-80 have participated in the formation of effective lubricating films. The reasonable lubrication mechanism of A-CDs stabilized by Span-80 was discussed based on the co-lubrication effect of Span-80 and A-CDs. The absorbing effect of Span-80 and the rolling and filling effects of A-CDs are all beneficial to the building of lubricating films, thereby tremendously boosting the lubricity of PAO4. The A-CDs stabilized by Span-80 are promising to become a kind of eco-friendly and high-performance lubricant additive for PAO.