The design and development of self-lubricating materials aid in enhancing the tribological performance and prolonging the service life of aero self-lubricating spherical plain bearings. Herein, monodisperse hollow mesoporous carbon nanospheres (HMCNs) with thin shell thickness and uniform particle size were synthesized. Afterward, oil-containing nanocapsules (Oil@HMCNs) were obtained by the impregnation method, which was an innovative approach to prepare nanoscale capsules. The Oil@HMCNs were monodispersed, and the oil content rate could reach 45 wt %. The nanocapsules were applied as additives to achieve the self-lubricating properties of epoxy resin (EP). It was revealed that the coefficient of friction (COF) and the wear rate of EP in dry friction can be decreased from 0.56 to 0.084 and from 50.15 × 10–6 to 0.27 × 10–6 mm3/N/m, respectively. The tribological properties of EP composites in dry friction are better than those of EP with external oil. According to the analysis of friction pairs, the antifriction performance was contributed by the released automatic transmission fluid 6HP (ATF6) from nanocapsules. Meanwhile, the presence of ATF6 effectively could inhibit fatigue wear, and the decrease of compressive strength and surface hardness led to plastic deformation and mechanical polishing. Both resulted in a lower wear rate of EP. In conclusion, this work explored the application possibility of hollow mesoporous materials in lubrication. The prepared EP composites exhibited excellent tribological performances and self-lubricating properties, which were expected to be applied to self-lubricating spherical plain bearings and other mechanical parts.

The water-based superlubricity can be promoted to a high-speed of 1.6 m s−1 after pre-running-in at low-speed of 0.075 m s−1.

Hydration lubrication by the hydrated surface-grafted macromolecules covering the joint cartilage is crucial for the proper functioning of natural synovial joints. However, when considering artificial replacements, similar surface-grafted polymers on artificial materials are usually insufficient for the long-term lubrication due to lack of stability and durability. In this work, an overall material modification through embedding polyelectrolyte brushes was performed for prolonged lifetime. Method-wise, hydrophilic monomer 3-sulfopropyl methacrylate potassium salt (SPMK) was grafted onto ultrahigh molecular weight polyethylene (UHMWPE) powders through photoinduced radical graft polymerization, followed by hot-press forming of the modified powders to afford homogeneous modified material. Trials revealed significantly increased surface wettability and negative charge density, giving rise to strong hydration lubrication that led to a stable and low friction coefficient of 0.009, and an ultralow wear rate of 9.1 × 10–8 mm3 (N m)−1 under physiological conditions, which could be consistently maintained even after the surface was sheared off with polishing equipment. This overall material modification on UHMWPE through polyelectrolyte embedment, applied to obtain long-lasting, highly lubricated materials, therefore presents a promising method for the preparation of artificial joints.

Water-based lubricants provide lubrication of rubbing surfaces in many technical, biological, and physiological applications. The structure of hydrated ion layers adsorbed on solid surfaces that determine the lubricating properties of aqueous lubricants is thought to be invariable in hydration lubrication. However, we prove that the ion surface coverage dictates the roughness of the hydration layer and its lubricating properties, especially under subnanometer confinement. We characterize different hydration layer structures on surfaces lubricated by aqueous trivalent electrolytes. Two superlubrication regimes are observed with friction coefficients of 10 −4 and 10 −3 , depending on the structure and thickness of the hydration layer. Each regime exhibits a distinct energy dissipation pathway and a different dependence to the hydration layer structure. Our analysis supports the idea of an intimate relationship between the dynamic structure of a boundary lubricant film and its tribological properties and offers a framework to study such relationship at the molecular level.

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