Fundamental understanding of the tribological and thermal behavior of Ag–MoS2 nanoparticle-based multi-component lubricating system

The objective of this study is to investigate the tribological and thermal properties of the recently developed Ag–MoS2 nanoparticle-based multi-component lubricating system. To obtain greater tribofilm durability and to enhance the tribological and thermal properties of MoS2, a chemo-mechanical processing method has been developed for the synthesis of composite silver nanoparticles (Ag NPs) incorporated into MoS2 nanoparticles (nMoS2). In order to characterize and investigate thermal and tribological behavior of the Ag–MoS2 hybrid system, four different Ag compositions were studied, ranging from 2 to 25 wt. % in MoS2. Different characterization techniques have been used to examine structural properties, silver content, particle size, and particle size distribution. The characterization results showed that the Ag NPs were successfully embedded into nMoS2 with particle sizes lower than 300 nm for 90% of agglomerated particles and 100 nm for most of de-agglomerated particles with no phase change of the system. The increase of internal strain of nMoS2 from the order of 0.002 to 0.02 was confirmed by XRD after the successful embedding of Ag NPs into nMoS2. In addition, the chemical and thermal analysis showed that silver molybdate was formed at temperatures above 450 °C, which demonstrates that this multicomponent system should be very effective for high temperature applications. The tribological tests revealed that nMoS2 – 2 wt. % Ag results in 15–20% reduction in friction under boundary lubricated sliding conditions and 30–37% reduction in wear. Therefore, the addition of Ag nanoparticles at an optimum concentration can significantly enhance the thermal and tribological performance of the developed Ag–MoS2 hybrid system.