Surface modification induced improvement of dispersion stability and tribological properties of MoS2 nanosheets

To alleviate the agglomeration and deposition of MoS2 nanofluid, MoS2 nanosheets were modified using self-made surface modifier. The self-made surface modifier was synthesized using triethanolamine (TEA) and stearic-acid (SA). Both total weight and mass ratio of TEA and SA were researched to gain modified MoS2 nanosheets with better dispersion stability. The modified MoS2 nanosheets prepared using surface modifier with optimal mass ratio and total weight were characterized by FT-IR and TEM. An organics solvation layer with a thickness of 15–17 nm was found adsorbed on MoS2 nanosheets, which prevented their agglomeration and improved their dispersion stability. Both four-ball tribotester and Molecular Dynamics simulation method were conducted to learn the effects of surface modification on the tribological properties of modified MoS2 nanofluid. The diffusion rate, interlayer distance, interlayer adsorption energy and shear stress of modified and unmodified MoS2 nanosheets were calculated. Due to interaction between MoS2 nanosheets and surface modifier, the interlayer distance of modified MoS2 nanosheets was increased. And the interlayer adsorption energy and interlayer shear stress were decreased, especially when the normal pressure was applied. The modified MoS2 nanosheets had not only better dispersion stability, but also excellent tribological properties.