Tuning the Surface Reactivity and Tribological Performance of Phosphonium-Based Ionic Liquid at Steel/Steel Interfaces by Bromide/Phosphate Anion Mixtures
Tuning the Surface Reactivity and Tribological Performance of Phosphonium-Based Ionic Liquid at Steel/Steel Interfaces by Bromide/Phosphate Anion Mixtures
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DOI：
10.1016/j.apsusc.2021.151245
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发表时间：
2021-09
影响因子：
6.7
通讯作者：
Zixuan Li;H. Celio;A. Dolocan;Nicolás Molina;Jude Kershaw;Oscar Morales-Collazo;J. Brennecke;F. Mangolini
中科院分区：
文献类型：
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作者：
Zixuan Li;H. Celio;A. Dolocan;Nicolás Molina;Jude Kershaw;Oscar Morales-Collazo;J. Brennecke;F. Mangolini
磷酸磷离子液体（ILs）具有良好的摩擦学性能和优异的热稳定性以及与矿物油和合成油的良好相容性，是一种很有前途的润滑油添加剂。在这里，我们评估的润滑性能的三己基十四烷基鳞（[P6，6，6，14]）为基础的离子液体时，用于钢/钢接触的双（2-乙基己基）磷酸盐（[DEHP]）和溴（Br-）阴离子的相对浓度的依赖性。结果表明，当[P6，6，6，14] Br与[P6，6，6，14][DEHP]体积比增加至0.2：1时，摩擦和磨损没有变化，而该比例的进一步增加导致摩擦和磨损降低。X射线光电子能谱和飞行时间二次离子质谱测量强调，IL的润滑性能对[P6，6，6，14] Br-与[P6，6，6，14][DEHP]比率的依赖性源于该IL的腐蚀性和表面反应性之间的平衡：而[DEHP]在非接触区作为缓蚀剂，含磷物质的形成由于磷离子的水解，磨损痕迹中的氧部分增加了磷的表面覆盖率。这被提议通过降低钢/钢接触处的粘附力和降低界面剪切强度来降低摩擦。
Phosphonium phosphate ionic liquids (ILs) are promising lubricant additives for engine oils owing to a combination of good tribological performance and attractive properties, such as high thermal stability and good miscibility with mineral and synthetic oils. Here, we evaluate the dependence of the lubricating performance of trihexyltetradecylphosphonium ([P6,6,6,14])-based ILs when used in steel/steel contacts on the relative concentration of bis(2-ethylhexyl)phosphate ([DEHP]) and bromide (Br-) anions. The results indicate no changes in friction and wear upon increasing the [P6,6,6,14]Br-to-[P6,6,6,14][DEHP] volume ratio up to 0.2:1, while a further increase in this ratio leads to a reduction of friction and wear. X-ray photoelectron spectroscopy and time-of-flight secondary ion mass spectrometry measurements highlight that the dependence of the lubricating properties of the ILs on the [P6,6,6,14]Br-to-[P6,6,6,14][DEHP] ratio originates from the balance between corrosivity and surface reactivity of this IL: while [DEHP] acts as corrosion inhibitor in the non-contact region, the formation of species containing phosphorus-oxygen moieties in the wear track as a result of the hydrolysis of phosphonium ions increases the surface coverage of phosphorus. This is proposed to decrease friction by decreasing adhesion at steel/steel contacts and lowering the interfacial shear strength.