Extremely low friction and wear enabled by 4-dodecylphenol functionalized magnesium oxide nanolubricant for steel tribopairs

Friction and wear are the main reasons for energy dissipation and the premature failure of mechanical assemblies; thus, it is desirable to achieve extremely low friction and wear in a variety of practical applications. The results in this work demonstrate that 4-dodecylphenol functionalized magnesium oxide (MgO) nanolubricant is capable of achieving extremely low friction (about 0.05) and wear rate (100 μm³/N·m) for bearing steel tribopairs. Magnesium oxide nanoparticles are well dispersed in base oil as 4-dodecylphenol could interact with particles through the phenol group via charge transfer. The superior tribological performance originates because MgO nanoparticles could exist stably between the friction interfaces, preventing the direct contacts of asperity peaks and reducing the real contact area. Furthermore, the interlayered MgO nanoparticles are also beneficial to smoothing the friction surfaces via the micro-polishing process, effectively reducing the specific contact pressure and hindering the occurrence of serious adhesive wear. Careful observation of the wear surfaces on tribopairs demonstrates the role of MgO nanoparticles in tribological performance improvement and the lubrication mechanism. Our result is beneficial to paving the way to the large-scale application of MgO nanolubricants and the realization of extremely low friction and wear.