State Key Laboratory of Tribology , Tsinghua University , Beijing 100084 , China.
ACS Appl Mater Interfaces. 2019 Feb 13;11(6):6568-6574. doi: 10.1021/acsami.8b21059. Epub 2019 Jan 30.
Several ionic liquids (ILs) are formed in situ with monovalent metal salts and ethylene glycol (EG). The macroscale superlubricity and antiwear properties of the ILs were studied between ceramic materials. Superlow coefficients of friction of less than 0.01 could be obtained for all ILs at silicon nitride (SiN) interfaces induced by tribochemical reactions. Notably, the IL ([Li(EG)]PF) formed with LiPF and EG exhibited the greatest superlubricity and antiwear properties. The results of film thickness calculations and surface analysis showed that the lubrication regime during the superlubricity period was the mixed lubrication, and a composite tribochemical layer (composed of phosphates, fluorides, silica (SiO), and ammonia-containing compounds), hydration layer, and fluid film contributed to superlubricity and wear protection. It was found that the small size of metal cations was beneficial for alleviating wear, and PF anions exhibited the smallest friction and best antiwear performance at SiN interfaces. This work studied the lubricity and antiwear properties of ILs with different cations and anions, enriching the range of alternative ILs for macroscale superlubricity and low wear, and is of importance to engineering applications.
几种离子液体（ILs）是由单价金属盐和乙二醇（EG）原位形成的。研究了 ILs 在陶瓷材料之间的宏观超滑和抗磨性能。在氮化硅（SiN）界面上，通过摩擦化学作用，所有 ILs 的摩擦系数都可以低至 0.01 以下。值得注意的是，由 LiPF 和 EG 形成的 IL([Li(EG)]PF)表现出最大的超滑和抗磨性能。薄膜厚度计算和表面分析的结果表明，在超滑期间的润滑状态是混合润滑，复合摩擦化学层（由磷酸盐、氟化物、二氧化硅（SiO）和含氨化合物组成）、水合层和流体膜有助于超滑和磨损保护。研究发现，金属阳离子的小尺寸有利于减轻磨损，PF 阴离子在 SiN 界面上表现出最小的摩擦和最佳的抗磨性能。这项工作研究了具有不同阳离子和阴离子的 ILs 的润滑性和抗磨性能，丰富了用于宏观超滑和低磨损的替代 ILs 的范围，对工程应用具有重要意义。
