Contrasting Roles of Water at Sliding Interfaces between Silicon-Based Materials: First-Principles Molecular Dynamics Sliding Simulations
Contrasting Roles of Water at Sliding Interfaces between Silicon-Based Materials: First-Principles Molecular Dynamics Sliding Simulations
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DOI：
10.1021/acs.jpcc.8b01953
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发表时间：
2018-05-17
影响因子：
3.7
通讯作者：
Kubo, Momoji
中科院分区：
文献类型：
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作者：
Ootani, Yusuke;Xu, Jingxiang;Kubo, Momoji
众所周知，硅基材料的磨损是由于在滑动界面与水的摩擦化学反应，但详细的机制仍存在争议。在这项研究中，我们使用第一性原理分子动力学方法来研究摩擦化学磨损机制。当滑动界面存在少量水时，观察到连接两个表面的界面桥键的形成。这些键将剪切力传递到表面，从而引起表面的应变。应变后的表面Si-O键随后与水发生反应（Si-O- si + H2O -> Si-OH + Si-OH），即发生水解反应。由于水解反应导致表面Si-O键离解，水促进了摩擦化学磨损。然而，当有大量的水存在时，它把两个表面分开了。因此，水抑制了界面桥键的形成，进而抑制了Si-O键的水解，从而抑制了摩擦化学磨损。我们的研究结果表明，水可以促进或抑制摩擦化学磨损，这取决于存在的量。我们认为，以前报道的硅基材料摩擦化学磨损的湿度依赖性可以用水的这些对比作用来解释。
It is known that the wear of silicon-based materials is due to the tribochemical reaction with water at the sliding interface, but the detailed mechanisms remain under debate. In this study, we used a first-principles molecular dynamics method to investigate the tribochemical wear mechanism. When a small amount of water was present at the sliding interface, the formation of interfacial bridge bonds connecting the two surfaces was observed. These bonds transmitted shear force to the surfaces that induced strain therein. The strained surface Si-O bonds subsequently reacted with water (Si-O-Si + H2O -> Si-OH + Si-OH), that is, the hydrolysis reaction occurred. Because the hydrolysis reaction resulted in dissociation of the surface Si-O bonds, water promoted tribochemical wear. However, when a large amount of water was present, it separated the two surfaces. The water thereby suppressed the formation of interfacial bridge bonds and in turn the hydrolysis of Si-O bonds and thus tribochemical wear. Our results indicate that water could either promote or suppress tribochemical wear, depending on how much was present. We suggest that the previously reported humidity dependence of the tribochemical wear of silicon-based materials can be explained in terms of these contrasting roles of water.