Reactive molecular dynamics (ReaxFF) simulations are performed to explore the tribological behavior between fully hydroxylated amorphous silica (a-SiO₂) surfaces as a function of surface silanol density. The results show that the interfacial friction and wear are greatly reduced by increasing surface silanol density, which originates from the suppression of the initial formation of interfacial Si–O–Si bridge bonds. Two different tribochemical reactions resulting in the formation of interfacial Si–O–Si bridge bonds are observed: i.e., one occurring between two silanol groups, which is insensitive to changes in silanol density, and the other occurring between a silanol group and a surface Si–O–Si bond, which is strongly suppressed with the increase of silanol density. We decouple the contributions of these two Si–O–Si bond formation mechanisms to the observed tribological behavior and find that the latter formation mechanism plays a dominant role. Furthermore, the changes in the geometry and structure of fully hydroxylated a-SiO₂ surface caused by the increased surface silanol groups also play an important role in the tribochemical reactions and the tribological performance of the a-SiO₂/a-SiO₂ system. This work provides a deeper insight into the effect of surface silanol groups on the tribological behaviors of silicon-based materials.

中文翻译：

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表面硅烷醇基对非晶二氧化硅表面之间摩擦和磨损的影响

进行反应分子动力学（ReaxFF）模拟以探索完全羟基化的无定形二氧化硅（a-SiO ₂）表面作为表面硅烷醇密度的函数。结果表明，通过提高表面硅烷醇密度可以大大降低界面摩擦和磨损，这是由于抑制了Si-O-Si桥键的初始形成。观察到两种不同的摩擦化学反应，导致形成界面Si–O–Si桥键：即，一个发生在两个硅烷醇基团之间，对硅烷醇密度的变化不敏感，另一个发生在硅烷醇基团和表面Si之间-O-Si键，随着硅烷醇密度的增加而受到强烈抑制。我们将这两种Si–O–Si键形成机理对观察到的摩擦学行为的贡献解耦，发现后者的形成机理起主要作用。此外，由增加的表面硅烷醇基团引起的₂表面在a-SiO ₂ / a-SiO ₂系统的摩擦化学反应和摩擦学性能中也起着重要作用。这项工作提供了更深入的了解表面硅烷醇基团对硅基材料的摩擦学行为的影响。