Effects of surface chemistry on the mechanochemical decomposition of tricresyl phosphate
Effects of surface chemistry on the mechanochemical decomposition of tricresyl phosphate
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表面化学对磷酸三甲苯酯机械化学分解的影响
DOI：
10.1039/d3cp05320b
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发表时间：
2024
影响因子：
3.3
通讯作者：
Ewen, James P.
中科院分区：
文献类型：
--
作者：
Ogbomo, Egheosa;Bhuiyan, Fakhrul H.;Latorre, Carlos Ayestarán;Martini, Ashlie;Ewen, James P.
润滑剂抗磨剂在摩擦表面形成的保护性摩擦膜是由机械力化学促进的离解反应引发的。对于许多重要的添加剂，如三甲酚磷酸(TCP)，在分子水平上对这些过程还没有很好的理解。需要进一步澄清的一个方面是表面性质对机械力化学分解的影响程度。在这里，我们使用带有反应力场的非平衡分子动力学(NEMD)模拟(ReaxFF)来研究在一定温度范围内在滑动的亚铁表面之间受限和加压的TCP分子的分解。我们比较了磷酸三钙在天然铁、碳化铁和氧化铁表面的分解情况。我们发现，所有表面上的TCP分子的分解速率都随着温度和剪应力的增加而指数增加，这意味着这是一个应力增强的热激活(SATA)过程。NEMD模拟中基础油分子的存在降低了剪切应力，进而降低了TCP分解的速率常数。铁表面的分解速度比碳化铁快得多，尤其是氧化铁。Bell模型的活化能、活化体体积和指前因子在铁和碳化铁表面相似，但在氧化铁表面有显著不同。这些发现为研究三聚氰酸酯的机械力化学分解提供了新的见解，并对高温高压环境下新型润滑油添加剂的设计具有重要的指导意义。
The growth of protective tribofilms from lubricant antiwear additives on rubbing surfaces is initiated by mechanochemically promoted dissociation reactions. These processes are not well understood at the molecular scale for many important additives, such as tricresyl phosphate (TCP). One aspect that needs further clarification is the extent to which the surface properties affect the mechanochemical decomposition. Here, we use nonequilibrium molecular dynamics (NEMD) simulations with a reactive force field (ReaxFF) to study the decomposition of TCP molecules confined and pressurised between sliding ferrous surfaces at a range of temperatures. We compare the decomposition of TCP on native iron, iron carbide, and iron oxide surfaces. We show that the decomposition rate of TCP molecules on all the surfaces increases exponentially with temperature and shear stress, implying that this is a stress-augmented thermally activated (SATA) process. The presence of base oil molecules in the NEMD simulations decreases the shear stress, which in turn reduces the rate constant for TCP decomposition. The decomposition is much faster on iron surfaces than iron carbide, and particularly iron oxide. The activation energy, activation volume, and pre-exponential factor from the Bell model are similar on iron and iron carbide surfaces, but significantly differ for iron oxide surfaces. These findings provide new insights into the mechanochemical decomposition of TCP and have important implications for the design of novel lubricant additives for use in high-temperature and high-pressure environments.