Wide-temperature lubrication of core-shell structured MoS₂-based composites enabled via the formation of amorphous molten layer and low-shear lamellar Bi₂S₃ and Bi₂MoO₆

Molybdenum disulfide (MoS₂) serves as an outstanding solid lubricant applied in harsh service conditions. However, enhancing its lubricating, antioxidative and anti-wear capabilities over a broader temperature range stills a formidable challenge, owing to its susceptibility to oxidation at high-temperature. In this work, we achieved superior wide-temperature lubrication from room temperature (RT) to 800 ℃ via the design of core-shell structure, with the introduction of Bi₂O₃ nanoparticles and encapsulation of SiO₂ shell, and phosphate as binder. At RT and 200 ℃, stable low friction was realized through the synergistic interlayer sliding of MoS₂ and in-situ formed Bi₂S₃ with low shear strength. At 400 ℃, the protective SiO₂ shell inhibited the oxidation of the core lubricating phase, thus enabling MoS₂ and Bi₂S₃ to retain their lubricating functionality. When the temperature exceeded 600 ℃, the remarkable enhancement in lubricating property (with a coefficient of friction of 0.13–0.16) was attributed to the synergy of phosphate molten-phase lubrication and low-shear lubricating phases (Bi₂S₃ and Bi₂MoO₆). An amorphous phosphate molten layer formed at high temperatures and constructed a readily shearable lubricating interface. Low-shear lamellar-chain structure Bi₂S₃, weak interlayer van der Waals forces reduced the sliding resistance. The distorted MoO₆ octahedral structure of Bi₂MoO₆ induced an enlarged interlayer distance and weakened interionic coupling, which enhanced shear capability and excellent high-temperature lubrication performance. This work provides some reference for improving wide-temperature-range lubricating capabilities of solid lubricating materials.