Macroscopic fast superlubrication achieved on steel surfaces by Tannic acid-modified black phosphorus as additives

Friction and wear shorten equipment lifespan and cause energy loss, nd superlubrication achieved on steel-to-steel surfaces remains challenging. By adding tannic acid-modified black phosphorus nanosheets (TA-BP) to the tartaric acid/glycolic acid mixture (TCA/EG), macroscopic superlubrication can be achieved on engineering steel surfaces in just 5   s. Compared to TCA/EG, the wear rate of friction pairs decreased by 99% to 1.68×10⁻ 10 mm 3 ·N -1 ·m -1 . Surface analysis revealed that TA-BP rapidly deposits on friction pair surfaces, decomposes TCA into carbon films, and forms a composite friction film with BP that exhibits ultra-low shear strength. This tribofilm further reduces friction coefficient through synergistic interaction with lubricants. The study provides new insights for developing super lubricants suitable for mechanical applications.