Tribochemical Mechanism of Amorphous Silica Asperities in Aqueous Environment: A Reactive Molecular Dynamics Study

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• 作者：Da-Chuan Yue ; Tian-Bao Ma ; Yuan-Zhong Hu ; Jejoon Yeon ; Adri C. T. van Duin ; Hui Wang ; Jianbin Luo
• 刊名：Langmuir
• 出版年：2015
• 出版时间：February 3, 2015
• 年：2015
• 卷：31
• 期：4
• 页码：1429-1436
• 全文大小：666K
• ISSN：1520-5827

文摘

Reactive molecular dynamics (ReaxFF) simulations are used to explore the atomic-level tribochemical mechanism of amorphous silica (a-SiO₂) in a nanoscale, single-asperity contact in an aqueous environment. These sliding simulations are performed in both a phosphoric acid solution and in pure water under different normal pressures. The results show that tribochemical processes have profound consequences on tribological performance. Water molecules could help avoid direct adhesive interaction between a-SiO₂ surfaces in pure water under low normal load. However, formation and rupture of interfacial siloxane bonds are obviously observed under higher normal load. In phosphoric acid solution, polymerization of phosphoric acid molecules occurs, yielding oligomers under lower load, and tribochemical reactions between the molecules and the sliding surfaces could enhance wear under higher load. The bridging oxygen atoms in silica play an important role in the formation of interfacial covalent bonds, and hydrogen is found to have a weakening effect on these bonds, resulting in the rupture during shear-related loading. This work sheds light on tribochemical reactions as a mechanism for lubrication and wear in water-based or other tribological systems.