Graphitic carbon nitride quantum dots as novel and efficient friction-reduction and anti-wear additives for water-based lubrication

Undeniably, advances in water-based nano-additives play a considerable role in energy conservation and pollution reduction accompanied by the resurgence of water-based lubricants. Graphitic carbon nitride quantum dots (g-CNQDs) have attracted remarkable attention in water-based lubricant additives owing to their strong designability, favorable mechanical property, and unique self-lubricating effect. Therefore, a series of different-sized g-CNQDs with good water dispersibility were expediently synthesized via a hydrothermal strategy and directly used as water-based lubricant additives. Tribological tests indicated that the tribological behaviors of the g-CNQDs-based additives displayed an obvious phenomenon of performance-dependent physical dimensions. With the introduction of g-CNQDs-based additives (1.0 wt%) into the water-based lubrication system, which friction-reduction, anti-wear, and load-supporting performances can be maximally increased by 45.5%, 94.0%, and 233.3%, respectively. Meanwhile, the long-term operating performance of the lubrication system can be promoted under high-load conditions. The formed tribo-film caused by tribo-chemical reaction integrated with the nano-lubrication effect of g-CNQDs collectively contributed to their good tribological performances.