Alkylamine-Grafted Molybdenum Disulfide Nanosheets for Enhanced Dispersion Stability and Lubricity Properties

The unique structure and ultralow interlayer shear strength give molybdenum disulfide (MoS2) materials a broad prospect for energy savings, economic benefits, and extended operating life of lubrication systems. Herein, we prepared an effective integration strategy to prepare novel small-sized and chemically grafted MoS2 to solve the problems of poor dispersibility and easy agglomeration of MoS2. The MoS2 powder was stripped and oxidized to generate active centers using acid oxidation and high-speed ultrasonic crushing to obtain two different types of alkylamine chemically, covalently grafted, oxidized MoS2 nanosheets as lubricant additives to achieve friction reduction and antiwear. The chemical changes and structural characteristics of different types of alkylamine molecules upon covalent interaction with oxidized MoS2 were investigated in detail by FTIR, XPS, TGA, XRD, and TEM analyses. The results showed that the alkylamine-grafted MoS2 oxide nanosheets had good dispersion in 15# industrial white oil, and friction experiments confirmed that the alkylamine-grafted MoS2 oxide (MoS2-O-OLA) nanosheets exhibited better friction and wear resistance such that, compared with pure 15# industrial white oil, the 0.02 wt % MoS2-O-OLA nanosheets could significantly reduce friction (36.2%) and wear (22.4%). The field-emission scanning electron microscopy (FESEM) and EDS analyses of the wear surface showed that MoS2-O-OLA nanosheets play an important role in improving tribological properties by generating interlayer slippage at the steel ball contact interface, thereby forming surface protection and a uniform oil film.