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

Abstract

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.

Graphical Abstract

Keywords:

• MoS₂ nanosheets
• surface modification
• tribological properties
• dispersion stability
• molecular dynamics simulation

Additional information

Funding

This work was supported by the National Natural Science Foundation of China under Grant No. 51874036; Beijing Municipal Natural Science Foundation under Grant No. 2182041 and Beijing Municipal Education Commission under Grant No. KM201911417002.