Macroscopic superlubricity achieved by polyacrylic acid modified Fe3O4 nanoparticles as additives

In this study, a stable macroscopic superlubricity state (COF about 0.005) after a short running-in period of 5 s under an ultra-high contact pressure of 1.45 GPa was achieved with the lubrication of polyacrylic acid modified Fe 3 O 4 nanoparticles as additives at the Si 3 N 4 /sapphire interface. The realization of superlubricity can be attributed to the detachment of polyacrylic acid molecules on the modified Fe 3 O 4 nanoparticles surface, which induced the tribochemical reaction between the polyacrylic acid molecules and friction surfaces, generating a tribofilm to prevent the direct contact of the friction pair and provide a low shear strength to reduce friction. The extremely low friction and wear induced by polyacrylic acid modified Fe 3 O 4 nanoparticles may contribute to the development of high-performance lubrication systems.