Synthesis and interfacial interaction of Ag2S quantum dots for enhancing the tribological behaviors of PTFE-based lubricating coatings

The small size and strong interfacial interaction are the key factor and challenge for quantum dots to play their reinforcing role as promising fillers of solid lubricating coatings. Herein, the minuscule Ag2S quantum dots (FQDs) of 1.71 nm with high dispersibility were synthesized via thermal decomposition of the precursor under the disturbance of polyamide-imide (PAI) molecules, and their interaction was investigated. Then the optimization of the mechanical and tribological properties of the polytetrafluoroethylene-based lubricating coatings depending on interfacial interaction was conducted, and their enhancement mechanisms were discussed. The results indicated that the PAI molecules were chemically adsorbed to the surface of the Ag2S FQDs and the interfacial interaction was improved based on the in-situ coordination reaction between the carboxyl group and Ag ions. The micro-hardness and wear life were thus increased by 45.70 % and 395.24 % compared with the original coating. Enhancing mechanical strength, inhibiting the frictional reaction of substrate and promoting the formation of sp2 carbon-based tribofilm were the crucial effects of Ag2S FQDs to improve the coating performance in terms of protection against friction and wear. The smaller size and strong interfacial interaction of Ag2S FQDs promoted the structural integrity and continuity of carbon-based tribofilm.