Phytic Acid-Modified Black Phosphorus Nanosheets Achieve Ultrahigh Load Bearing and Rapid Superlubrication on Engineered Steel Surfaces

Achieving superlubrication on engineered steel surfaces is critical to reduce friction and wear in mechanical engineering. Herein, a lubricant with rapid superlubrication properties is designed by phytic acid (PA) modified black phosphorus (BP) nanosheets (PA-BP) into a mixture of poly (aspartic acid) (PASP) and ethylene glycol (EG) solution (PASP/EG). It is able to achieve a superlubrication state (µ ≈ 0.0048) at a high contact pressure of 710 MPa on the engineered steel surface and the time to reach superlubrication (tRs) is only 26 s. The addition of PA-BP could reduce wear rate by 96% on the steel surface (1.51×10⁻¹⁰ mm³ N⁻¹ m⁻¹) compared to the lubrication of PASP/EG. The surface analysis and molecular dynamics simulations show that PA-BP nanosheets are easily adsorbed on the steel surface to form an adsorbent tribofilm. These PA-BP nanosheets occur oxidation during the friction process, which could adsorb water molecules in PASP/EG to form a water layer with a thickness of 18 Å. This leads to the transformation of the shear interface into water layer with low shear strength, thus achieving the rapid superlubrication at high contact pressure. This work provides a new idea for the design of rapid macroscopic superlubrication on engineered steel surfaces for industrial applications.