Effect of Anionic Alkyl Chain Length on Tribological Properties of Ionic Liquids: Molecular Dynamics Simulations

IF 2.9 3区工程技术 Q2 ENGINEERING, CHEMICAL

Tribology Letters Pub Date : 2024-04-05 DOI:10.1007/s11249-024-01843-7

Zhen Ma, Fangli Duan

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Abstract

Ionic liquids (ILs) are widely adopted as lubricating materials in engineering fields for steel sliding contacts, and the adsorption structure and kinematic state of friction surfaces are crucial for understanding the improvement of tribological properties in experiments. In this study, we employed molecular dynamics methods to examine the structure and shear dynamics of five ILs with the same cationic triethanolamine paired with carboxylate anions of different alkyl chain length, confined between two crystalline iron surfaces. The results show that the chain length of anions influence the quantity of hydrogen bonds formed, the distribution on the iron surfaces, the thickness of the adsorption layers during the sliding process and the overall motion state. Under elastohydrodynamic lubrication conditions, ILs with longer alkyl chain exhibit less friction on a macroscopic scale due to the weaker hydrogen bonds between the anions and cations, the formation of thicker adsorption layers between sliding surfaces, and the overall pronounced layering phenomenon. These atomic insights into the structure and state of motion during friction can help promote the use of ILs as lubricating materials in engineering applications.

Graphical Abstract

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阴离子烷基链长对离子液体摩擦学特性的影响：分子动力学模拟

在工程领域，离子液体（ILs）被广泛用作钢材滑动接触的润滑材料，而摩擦表面的吸附结构和运动状态对于了解实验中摩擦学性能的改善至关重要。在本研究中，我们采用分子动力学方法研究了五种具有相同阳离子三乙醇胺与不同烷基链长的羧酸根阴离子配对的 ILs 在两个结晶铁表面之间的结构和剪切动力学。结果表明，阴离子的链长会影响形成的氢键数量、在铁表面的分布、滑动过程中吸附层的厚度以及整体运动状态。在弹性流体动力润滑条件下，烷基链较长的 IL 在宏观尺度上表现出较小的摩擦力，这是因为阴离子和阳离子之间的氢键较弱，在滑动表面之间形成较厚的吸附层，以及整体上明显的分层现象。对摩擦过程中的结构和运动状态的这些原子洞察有助于促进在工程应用中将ILs用作润滑材料。

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来源期刊

Tribology Letters 工程技术-工程：化工

CiteScore

5.30

自引率

9.40%

发文量

116

审稿时长

2.5 months

期刊介绍： Tribology Letters is devoted to the development of the science of tribology and its applications, particularly focusing on publishing high-quality papers at the forefront of tribological science and that address the fundamentals of friction, lubrication, wear, or adhesion. The journal facilitates communication and exchange of seminal ideas among thousands of practitioners who are engaged worldwide in the pursuit of tribology-based science and technology.