Exploring the Physical Limits of Structural Superlubricity

这项资助将集中在“结构超润滑性”上，这是一种特殊的现象，在这种现象中，两个物体之间的摩擦几乎消失，而不使用任何润滑剂。摩擦是机械系统和过程中有用能量损失的主要原因，对国家能源需求产生巨大影响。事实上，最近的估计表明，与摩擦相关的经济损失可能高达美国等发达国家国内生产总值的百分之几。为减少摩擦而设计的新方法对保护有用能源以及经济和环境的可持续性具有重要意义。结构超润滑性就是这样一种方法，最近已经在实验上证明了微观接触。该研究项目将探索结构超润滑性在运动速度，操作温度和接触尺寸方面的物理限制，以确定该想法是否可以用于在实际相关的机械系统中建立超低摩擦滑动。该项目有一个重要的多样性组成部分，因为它将在加州大学默塞德，西班牙裔服务机构，其中许多学生是第一代进行。研究工作还将通过针对圣华金河谷社会经济服务不足地区的K-12学生的外联活动来补充。该项目的总体目标是形成对结构超润滑性的物理极限的基本理解，即其对温度和滑动速度等操作条件变化的鲁棒性，以及超低摩擦状态可以保持的长度尺度。为了实现这一目标，将进行基于原子力显微镜的操作实验，从而使金薄片在原子级平坦的石墨衬底上横向移动，并以高精度记录相关的摩擦力。实验将在不同的温度下进行，滑动速度，并在接近微米制度的大小的薄片。所获得的结果将为尚处于萌芽阶段的结构超润滑性物理限制理论提供关键的实验数据。该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

This grant will focus on “structural superlubricity”, a peculiar phenomenon where friction between two objects nearly vanishes, without the use of any lubricants. Friction is the leading cause of useful energy loss in mechanical systems and processes, with an enormous impact on national energy demand. In fact, recent estimates indicate that economic losses associated with friction can amount up to a few percent of the gross domestic product of a developed nation such as the USA. New methods devised to mitigate friction have important implications for the conservation of useful energy, as well as economic and environmental sustainability. Structural superlubricity is one such method, which has been recently experimentally demonstrated for microscopic contacts. This research project will explore the physical limits of structural superlubricity in terms of speed of motion, operation temperature, and contact size, to determine if the idea can be employed to establish ultra-low friction sliding in mechanical systems of practical relevance. The project has a significant diversity component, as it will be conducted at UC Merced, a Hispanic Serving Institution where many students are first-generation. The research efforts will be additionally complemented by outreach activities aimed at K-12 students in the socio-economically underserved region of San Joaquin Valley. The overarching objective of the project is to form a fundamental understanding of the physical limits of structural superlubricity, in terms of its robustness against changes in operating conditions such as temperature and sliding speed, as well as the length scale up to which the ultra-low friction state can be preserved. To achieve this objective, manipulation experiments based on atomic force microscopy will be performed, whereby gold flakes will be laterally moved on top of atomically flat graphite substrates and the associated friction forces will be recorded with high precision. Experiments will be performed at different temperatures, sliding speeds, and on flakes of sizes approaching the micrometer regime. The obtained results will provide crucial experimental data for the still nascent theories about the physical limitations of structural superlubricity.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.