Preparation and tribological properties of oleic acid-decorated MoS2 nanosheets with good oil dispersion

In this paper, the self-made two-dimensional MoS2 nanosheets with five-layer thickness were attempted to be modified with oleic acid (OA) with a simple one-step route, denoted OA-MoS2. The OA-MoS2 nanosheets were confirmed by a series of characterizations. The results showed that OA molecules could chemically seal MoS2 nanosheets through C-S bonds, which significantly improved the dispersibility and stability of MoS2 nanosheets in base oil. The OA-MoS2 nanosheets possessed better dispersibility in base oil and could maintain the stability in oil up to 96 h. Furthermore, the tribological properties of OA-MoS2 nanosheets as an additive in base oil were completely studied through a ball-on-ball configuration four-ball testing machine. The experimental results showed that the average friction coefficient and average wear scar diameter of the 0.04 wt.% OA-MoS2-based oil were decreased by about 41.2% and 17.1% as compared to base oil, respectively. In addition, its extreme pressure performance increased by about 13.0%. These results indicated that OA-MoS2 nanosheets exhibited better antifriction, antiwear and extreme pressure abilities in oil due to the desirable solved dispersibility.