Turbulence-Like Cu/Mos2 Films: Structure, Mechanical And Tribological Properties

The application of pure molybdenum disulfide (MoS2) film as solid lubricant is limited due to its low hardness and high friction coefficient in the atmosphere. It is reported that the hardness can be improved by doping metal elements into MoS2, while the friction coefficient can be reduced by the formation of curved micro-nano structure of MoS2. Thus, doping metal atoms with catalytic properties such as Cu into MoS2, to form turbulence-like micro-nano structure has the potential to simultaneously increase hardness and decrease friction coefficient. In our work, we deposit Cu/MoS2 films with turbulence-like structure (TL-MoS2) using magnetron sputtering technology, which exhibit higher hardness and lower friction coefficient in the atmosphere than pure MoS2. When the Cu content reaches 15.9 at.%, Cu atoms with catalytic properties induce the formation of curved S-Mo-S layers and forms TL-MoS2. Cu incorporation results in the change of preferred orientation of film from (100) plane for pure MoS2 to (002) plane for Cu/MoS2, accompanied by the densification of the structure. The hardness of Cu/MoS2 is approximately 10 times higher than that of pure MoS2 due to the denser structure and TLMoS2. It is worth mentioning that TL-MoS2 contributes to the improvement of the hardness by extending the strength of the planar network into a three-dimension space network. Moreover, TL-MoS2 prevents oxidation and promotes the formation of MoS2 tribofilm during sliding, leading to a significant reduction of the friction coefficient to 0.07 +/- 0.01 in the atmosphere, which is 3 times lower than that of pure MoS2 film. Our strategy provides guidance for preparing metal doped MoS2 films with excellent mechanical and tribological properties for application in the atmosphere.