Characterization of ionic liquid films in view of tribological properties and development of structure-property relationships by means of electrochemical surface force apparatus

本研究项目的目的是表征和检查离子液体薄膜在不同层上的摩擦学行为。摩擦学，或研究相互接触的表面滑动，在我们的日常生活中具有实际意义，并具有极大的经济意义。测量到的两个物体之间的摩擦力是原子尺度上表面累积相互作用的结果。特别是，界面的物理和化学性质决定了摩擦行为。由于离子液体的独特特性，包括在固体表面前形成层状结构，它们是未来高性能润滑剂的理想候选者。在这个研究项目中，纳米和微米尺度的实验将在英国牛津大学进行，使用表面力装置对样品进行完全电化学控制。电化学方法集成的优点是可以改变关键参数，如衬底的粗糙度以及离子液体层的稳定性和排列，可逆和原位。这个项目的主要目标是了解固体-液体界面的构成，作为距离表面几纳米内的滑动平面。为了在分子长度尺度上发展结构-性能关系，机械性能将以高分辨率进行探测。对离子液体的摩擦特性的初步研究已经在牛津大学和申请人进行了。基于这些结果，离子液体的特定性质，包括阴离子和阳离子的大小，烷基链的电荷数和长度以及底物的特征，例如表面粗糙度会发生变化；此外，还计划用水和盐控制离子液体的污染，以研究它们对摩擦性能的影响。本研究计划所描述的基础研究对于离子液体摩擦学应用的建立至关重要。

The goal of this research project is to characterize and examine the tribological behaviour on different layers of thin films of ionic liquids. Tribology, or the study of surfaces in contact sliding against each other is of practical relevance in our everyday life and of utmost economical importance. The measured friction force between two bodies is a result of cumulative interactions of the surfaces on the atomic scale. In particular, the physical andchemical properties of the interface determine the frictional behavior. Due to the unique properties of ionic liquids, including the formation of a layered structure in front of solid surfaces, they are ideal candidates for tomorrows high-performance lubricants. Within this research project experiments at the nano- and micrometer scale will be performed at the University of Oxford in the United Kingdom using a surface force apparatus operating with full electrochemical control of the sample. The advantage of the integration of electrochemical methods is the possibility to alter key parameters such as the roughness of the substrate as well as the stability and arrangement of the ionic liquid layers reversibly and in situ. The primary objective of this project is to understand the constitution of the solid-liquid interface as the sliding plane within the first few nanometers apart from the surface. The mechanical properties will be probed with a high force resolution as required to develop structure-property relationships on the molecular length-scale. Preliminary studies into the frictional properties of ionic liquids have already been carried out at Oxford and by the applicant. Based on these results specific properties of the ionic liquids, including the size of the anions and cations, the charge number and the length of the alkyl chain as well as characteristics of the substrate, e.g. the surface roughness will be varied; furthermore, the controlled contamination of the ionic liquids with water and salts is planned to examine their effect on the friction properties. The fundamental research described in this research proposal is crucial for the establishment of tribological applications of ionic liquids.