Background

Ionic liquids (ILs) have recently attracted considerable attention in tribology owing to their unique physico-chemical properties and promising lubrication performance when used in a wide range of material pairs. 

Objective

The aim of this review article is to summarize recent advances in our knowledge related to the lubrication mechanisms of neat ILs, with a particular focus on nanoscale studies dealing with the behavior of ILs in the boundary lubrication regime.

Methods

We first discuss the current state-of-the-art concerning the normal pressure-dependent lubrication mechanism of ILs and then focus on the dynamic behavior of ILs upon nanoconfinment. Finally, we summarize recent research efforts aiming to control the tribological response of ILs by changing the surface charge density, evaluate the effects of impurities on the lubricity of ILs, and shed light on the IL tribochemistry at small length scales.

Results

While the field of IL-mediated lubrication has made significant progress, several open questions still remain, including the effects of temperature, impurities, and surface roughness on the friction response and dynamic behaviors of nanoconfined ILs. Additionally, a mechanistic understanding of the tribochemical reactivity of ILs is still lacking.

Conclusions

To harness the full potential of ILs for tribological applications, significant work is still required to establish links between the IL structure, lubrication mechanism(s), and performance. These advancements will be instrumental for the predictive design, development, and implementation of ILs with enhanced tribological properties in next-generation lubricants for a variety of applications across several sectors, including manufacturing and transportation.

中文翻译：

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离子液体纳米摩擦学的最新进展

背景

离子液体（ILs）由于其独特的理化特性和在多种材料对中使用时具有良好的润滑性能，最近在摩擦学中引起了广泛的关注。 

客观的

这篇综述文章的目的是总结与纯净ILs润滑机理有关的最新知识进展，特别关注处理边界润滑方案中ILs行为的纳米级研究。

方法

我们首先讨论有关IL的正常压力相关润滑机制的最新技术，然后重点关注纳米约束下IL的动态行为。最后，我们总结了最近的研究成果，旨在通过改变表面电荷密度来控制IL的摩擦学响应，评估杂质对IL润滑性的影响，并阐明小长度尺度上的IL摩擦化学。

结果

尽管IL介导的润滑领域取得了长足的进步，但仍然存在一些悬而未决的问题，包括温度，杂质和表面粗糙度对纳米约束IL的摩擦响应和动力学行为的影响。另外，仍然缺乏对IL的摩擦化学反应性的机械理解。

结论

为了充分利用IL的摩擦学潜力，仍需要大量工作来建立IL结构，润滑机制和性能之间的联系。这些进步将有助于在下一代润滑剂中具有增强的摩擦学性能的IL的预测性设计，开发和实施，从而适用于包括制造和运输在内的多个部门的各种应用。