CAREER: Linking Molecular Structure and Lubrication Mechanism in Halogen-Free, Boron-Based Ionic Liquids

该学院早期职业发展（CAREER）计划资助支持离子液体（IL）的基础研究，离子液体是具有可调组成和熔点低于100ºC的盐。由于离子液体具有独特的性质和良好的润滑性能，因此在绿色制造技术中具有广阔的应用前景。使用IL用于润滑目的的一个关键挑战是缺乏对IL分子结构和润滑性能之间关系的理解。该基金支持旨在填补这一知识空白的基础研究，通过确定一类摩擦学上有前途的IL的润滑机制，即无卤素，硼基IL（hf-BILs），并建立其分子结构和摩擦学特性之间的联系。从该项目中获得的新知识使具有增强润滑性能的离子液体的合理设计成为可能，这将有助于通过提高加工过程的可持续性和效率来提高美国的工业生产力和竞争力。该项目的研究目标的补充是教育计划，这将增加退伍军人在STEM计划的包容性，并与小学教师合作，以增加K-5学生接触科学和工程。该研究项目解决了两个主要的开放性问题，在使用IL润滑目的：a）IL的润滑性能对IL化学的依赖性; B）IL在滑动界面处的应力诱导的热活化反应、所得表面反应层的化学/结构和IL分子结构之间的相互关系。这项研究涉及的IL的合成与系统的不同组成，这是用于在原位原子力显微镜实验，涉及定义明确，单一的粗糙滑动接触。这个实验框架测试的假设，牺牲，低剪切强度层在滑动界面的增长率与正常的应力和温度呈指数增加，但显着影响IL分子结构。反应层的化学和纳米机械性能的非原位表征揭示了hf-BILs中的化学变化，它们在滑动界面的化学反应性和摩擦诱导反应层的性质之间的相互关系。这项研究的结果有助于在先进制造方法的下一代润滑剂中实现具有增强摩擦学性能的IL的预测性设计、开发和实施。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 Faculty Early Career Development (CAREER) Program grant supports fundamental research on ionic liquids (ILs), which are salts with tunable composition and melting point below 100ºC. Owing to their unique properties and good lubrication performance, ILs are promising additives for cutting fluids used in green manufacturing approaches. A critical challenge in the use of ILs for lubrication purposes is the lack of understanding of the relationship between IL molecular structure and lubrication performance. This grant supports fundamental research aiming to fill this knowledge gap by identifying the lubrication mechanism(s) of a class of tribologically-promising ILs, namely halogen-free, boron-based ILs (hf-BILs), and establishing links between their molecular architecture and tribological properties. The new knowledge emerging from the project enables the rational design of ILs with enhanced lubrication performance, which will contribute to increasing the U.S. industrial productivity and competitiveness by improving the sustainability and efficiency of machining processes. Complementary to the research goal of this project are the educational programs which will increase the inclusion of veterans in STEM programs and collaborate with elementary school teachers to increase the exposure of K-5 students to science and engineering.The research project addresses two major open questions in the use of ILs for lubrication purposes: a) the dependence of the lubrication performance of ILs on the IL chemistry; b) the interrelationship between the stress-induced, thermally-activated reactions of ILs at sliding interfaces, the chemistry/structure of the resulting surface reaction layers, and IL molecular structure. The study involves the synthesis of ILs with systematically varied composition, which are used in in situ atomic force microscopy experiments involving well-defined, single asperity sliding contacts. This experimental framework tests the hypothesis that the growth rate of sacrificial, low-shear-strength layers at sliding interfaces increases exponentially with normal stress and temperature but is significantly affected by the IL molecular structure. The ex situ characterization of the chemistry and nanomechanical properties of the reaction layers shed light on the interrelationship between chemical changes in hf-BILs, their chemical reactivity at sliding interfaces, and properties of the tribologically-induced reaction layers. The findings of this study are instrumental in enabling the predictive design, development, and implementation of ILs with enhanced tribological properties in next-generation lubricants for advanced manufacturing methods.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.