Dynamic chemisorption and tribochemistry of α-lipoic-acid-ester on ferrous surfaces

Tribofilm formation and growth play a vital role in friction reduction and antiwear enhancement. However, our understanding at the atomic level, particularly from a tribochemical viewpoint, is limited. Here, we elucidate α-lipoic acid ester tribofilm formation on ferrous interfaces using reactive molecular dynamics simulations. Our findings uncover a sequence where chemisorbed films initially develop through Fe-S bonding, followed by decomposition (C-O, C-S bonds) and polymerization reactions (S-S, S-O bonds). Thermal and mechanical forces collaboratively facilitate this process. The kinetic analysis demonstrates elevated activation volume exhibited a negative correlation with the reaction frequency difference. Normal stress boosts reactivity by encouraging the polymerization and reducing activation energy. This work offers a comprehensive understanding of α-lipoic acid ester tribofilm formation on ferrous interfaces.

摩擦膜（tribofilm）的形成与生长在减摩与抗磨性能提升中发挥着关键作用。然而，当前学界在原子尺度上对其的认知仍存在局限，尤其从摩擦化学（tribochemical）视角出发的相关认知尚且不足。本文借助反应分子动力学（reactive molecular dynamics）模拟，阐明了铁基界面上α-硫辛酸酯摩擦膜的形成过程。研究结果揭示了一条完整的演化序列：首先通过Fe-S键合形成化学吸附膜，随后发生C-O、C-S键的分解反应以及S-S、S-O键参与的聚合反应。热力与机械力的协同作用推动了该过程。动力学分析表明，活化体积（activation volume）的增大与反应频率差呈负相关关系；法向应力可通过促进聚合反应、降低活化能（activation energy）来提升反应活性。本研究为铁基界面上α-硫辛酸酯摩擦膜的形成机制提供了全面的认知。