Temperature-dependent tribological mechanisms of MoS2@SiO2 core-shell lubricants from 200 to 800 ℃: Experiments and molecular dynamics

Molybdenum disulfide (MoS 2 ) is an effective layered solid lubricant, but its rapid oxidation in air at elevated temperatures disrupts low-shear basal-plane sliding and causes unstable friction and accelerated wear. Here, a MoS 2 -core/SiO 2 -shell architecture, denoted as MoS 2 @SiO 2 , was fabricated through hydrothermal synthesis followed by a modified Stöber coating process. Its tribological behavior was systematically compared with that of uncoated MoS 2 over a temperature range of 200-800 °C, together with worn-surface characterization and molecular dynamics simulations. At 200 °C, both materials exhibited an average friction coefficient of approximately 0.05. At 400 °C, the friction coefficient of pure MoS 2 increased above 0.40, whereas that of MoS 2 @SiO 2 remained near 0.35; meanwhile, the maximum wear-scar depth decreased from approximately 16 to 11 μm. At 600 °C, MoS 2 @SiO 2 evolved toward a comparatively stable friction coefficient of approximately 0.40, whereas pure MoS 2 initially reached approximately 0.45 and exhibited pronounced oxidation-related instability. This friction stabilization was accompanied by sacrificial damage to the SiO 2 shell, indicating a temperature-dependent trade-off between interfacial protection and material loss. At 800 °C, MoS 2 @SiO 2 maintained a stable friction coefficient of approximately 0.25, lower than the approximately 0.30 measured for pure MoS 2 , and reduced the maximum wear-scar depth from approximately 3.2 to 2.2 μm. SEM/EDS observations indicate the formation of a continuous Si/O-rich tribofilm containing residual Mo/S species. Molecular dynamics simulations further show that shell fracture releases MoS 2 nanosheets, while SiO 2 fragments suppress stick-slip motion and redistribute interfacial energy. These results reveal a temperature-dependent transition from oxidation-barrier-assisted lubrication at 400-600 °C to a shear-assisted solid-viscous-film lubrication regime at 800 °C, providing a core-shell strategy for extending the operating-temperature window of MoS 2 -based solid lubricants.