Nanoscale Investigation of the Surface Reactivity of Ionic Liquids under Harsh Tribological Conditions

由于摩擦和磨损导致的移动机械部件的能源和资源损失给国民经济带来了巨大的成本（在英国，每年由摩擦和磨损造成的经济影响估计约占国内生产总值的2%，即250亿英镑）。作为一个特别的例子，乘用车使用的燃料中有三分之一用于克服发动机、传动装置、轮胎和刹车中的摩擦。对于一辆乘用车来说，这相当于每年大约340升的燃料，根据英国2015年的平均汽油价格，用于克服摩擦损失的成本为380英镑。这导致了能源的浪费和不必要的环境排放。因此，探索新型节能、环保的润滑油，以减少发动机、涡轮机、微电子等的摩擦和磨损，变得越来越重要。特别是，它将是试图实现2015年联合国气候变化公约设定的减少温室气体排放这一具有挑战性的环境目标的关键因素。以乘用车为例，欧洲环境和交通部长为2025年设定的新燃油效率目标，即每公里95克二氧化碳（相比之下，2014年的平均值为每公里123克二氧化碳），对科学家和工程师构成了巨大的挑战，他们现在需要开发新的技术解决方案和功能材料，以提高汽车效率，减少对环境的影响。本研究的研究将通过对一类“绿色”润滑剂（即离子液体）的有前途的特性的物理化学基础提供新的见解，从而有助于实现这一目标。离子液体最近被合成并提出作为传统润滑剂或润滑剂添加剂的替代品，用于各种应用，包括汽车发动机，微机电系统，硬盘和航空航天。例如，ILs的低挥发性使其成为发动机润滑油添加剂的吸引力，因为它不会产生有害的挥发性化合物，从而避免了废气后处理系统中的堵塞过滤器和催化剂降解，这是现有润滑油添加剂所关注的问题。在本研究过程中，将通过纳米尺度研究一类ILs（咪唑磺酸烷基/磷酸盐）在机械接触和剪切应力下在固体表面上的分子反应性，从而对其作用机制有一个基本的了解。为了实现这一目标，将使用一种新的方法方法，该方法基于最先进的表面分析技术，具有卓越的灵敏度和空间分辨率（包括基于同步加速器的技术）。这项研究的结果为合理设计具有特定任务性能的改性润滑油提供了一个起点，可以合成适用于各种工业应用（例如，汽车、航空航天、微电子）的节能、环保润滑油，并可以通过减少摩擦学对经济和环境的影响来提高可持续性。

Energy and resource losses in moving mechanical components as a result of friction and wear impose an enormous cost on national economies (in the UK the economic impact caused each year by friction and wear is estimated to be ~2% of the gross domestic product, i.e., £25 billion). As one particular example, one-third of the fuel used in passenger cars is employed to overcome friction in the engine, transmission, tyres, and brakes. For a single passenger car, this corresponds to approximately 340 litres of fuel per year, at a cost of £380 according to the average UK gas price in 2015, being spent in overcoming frictional losses. This results in wasted energy and unnecessary environmental emissions. The exploration of new classes of energy-efficient, environmentally-compatible lubricants, which can reduce friction and wear in engines, turbines, microelectronics, etc., is thus becoming increasingly important. In particular, it will be a key factor in attempting to achieve the challenging environmental objective of reducing greenhouse gas emission set during the 2015 UN Climate Change Convention. In the case of passenger cars, as an example, the new fuel efficiency target set by European environment and transport ministers for 2025, i.e., 95 g of CO2 per km (for comparison, the average value in 2014 was 123 g CO2 per km), constitutes a great challenge for scientists and engineers, who are now required to develop novel technical solutions and functional materials to improve car efficiency and decrease their environmental impact. The research in this study will contribute to this by providing novel insights into the physico-chemical basis underlying the promising properties of a class of "green" lubricants, namely ionic liquids (ILs), which have been recently synthesized and proposed as replacements of traditional lubricants or lubricant additives for a variety of applications, including automobile engines, microelectromechanical systems, hard disks, and aerospace. As an example, the low volatility of ILs makes them attractive as additives for engine oils, since the generation of no hazardous volatile compounds avoids blocking filters and catalyst degradation in the exhaust after-treatment systems, a concerning issue for existing lubricant additives. During the course of this research, a fundamental understanding of the mechanism of action of a class of ILs (imidazolium alkyl sulphate/phosphate) will be developed through the nanoscale investigation of their molecular reactivity on solid surfaces under mechanical contact and shear stress. To achieve this, a novel methodological approach, which is based on state-of-the-art advanced surface-analytical techniques with exceptional sensitivity and spatial resolution (including synchrotron-based techniques), will be used. The outcomes of the research, providing a starting point for rationally designing modified ILs with task-specific performance, can lead to the synthesis of energy-efficient, environmentally-friendly lubricants that are suitable for a variety of industrial applications (e.g., automotive, aerospace, microelectronics) and that can enhance sustainability through the reduction of the economic and environmental impact of tribology.