High contact stress phase transition structural superlubricity

Superlubricity refers to the state in which friction and wear almost disappear in the interface. Phase transition structural superlubricity (PTSS) is the superlubricity state achieved in liquid-solid interface by contact stress inducing liquid-solid phase transition of the lubricating medium. However, thus far, the maximum Hertz contact stress of PTSS currently realized is only approximately 600 MPa. In this study, PTSS with Hertz contact stress up to 1.313 GPa was achieved at the liquid-solid interface by constructing in situ heterojunction between the solid phase 1-dodecanol molecular layer and the graphene crystalline boundary tribofilm. By covalently modifying graphene with polydopamine, the adsorption capacity of graphene and SiC substrate was significantly enhanced, leading to the growth of crystalline boundary tribofilm with a thickness of 180∼200 nm. In addition, when the contact stress is greater than 137 MPa, 1-dodecanol will undergo liquid-solid phase transformation phenomenon. Solid phase 1-dodecanol molecules self-assemble to form a herringbone-like configuration by forming hydrogen bonds between the hydroxyl groups. These insights provide a novel method for realizing structural superlubricity and bridge the realms of solid superlubricity and liquid superlubricity.