Effects of oxidation-assisted grafting of MoS2 on tribological performance of steels

This research investigates the interfacial phenomenon of two-dimensional MoS2 particles through controlled oxidation and subsequent dodecylamine (DDA) functionalization. Experimentally, MoS2 was oxidized and grafted with DDA to tune the particle's surface properties and improve dispersion stability. Rheological studies revealed that oxidation improved MoS2's interaction with the polyalphaolefin (PAO) base oil, while DDA functionalization further enhanced its flow behavior and suspension stability. Tribological assessments indicated that oxidation alone notably reduced friction and wear of steel rubbing pair. The subsequent functionalization with DDA provided additional improvements, particularly in wear resistance, achieving a remarkable 93 % reduction compared to the base oil. Density functional theory (DFT) calculations confirmed that oxidation increased surface energy, promoting stronger adhesion. SEM analysis corroborated these findings, revealing significantly smoother wear surfaces and reduced material loss, particularly for DDA-functionalized oxidized MoS2 (DDA-Ox-MoS2). These results provide fundamental insights into how controlled oxidation and functionalization synergistically enhance the interfacial interaction of MoS2 and metal rubbing surfaces. This work offers a new understanding for developing high-performance lubricant additives with superior wear resistance.