GOALI: Enabling Ultra-Low Viscosity Lubricants Through Fundamental Understanding of Additive Interactions and Tribofilm Growth Mechanisms: An In-Situ Study

汽车发动机油通常包括几种不同的性能添加剂，每一种添加剂在提高燃油效率和发动机可靠性方面都起着至关重要的作用。通常添加到这类润滑油中的添加剂类型之一是抗磨添加剂，当汽车发动机内的不同部件之间发生金属对金属接触时，需要抗磨添加剂来减少磨损和故障。其中一种添加剂是一种基于锌、硫、磷、氧和碳氢化合物组合的分子，它在减少磨损方面非常有效，而且生产成本低廉，几乎用于每一种汽车发动机油。这种分子的工作原理是在发动机内的某些接触点形成表面膜。这些薄膜作为底层金属部件的保护垫，保护它们不受磨损。尽管它被广泛使用，但目前还不清楚这种分子是如何产生这些保护膜的。汽车润滑油的配方越来越低，粘度更低，有助于提高燃油经济性，减少不良排放。不幸的是，用于配制这些低粘度油的分子会干扰抗磨分子S生成保护膜并提供足够的磨损保护的能力。这项GOALI学术联络机会(GOALI)研究旨在通过使用新的纳米技术方法来提高我们对抗磨保护膜是如何形成以及它们的形成如何受到与其他类型的添加剂相互作用的影响的理解，从而为解决这一问题做出贡献。这项研究的结果将为下一代汽车润滑油的设计提供参考，因此将通过改善节能、减少与维护相关的成本和减少不良排放对美国经济产生直接影响。在这项研究中，将利用宾夕法尼亚大学最近开发的新的原位原子力显微镜方法，对抗磨摩擦膜形成机理进行定量的动力学和热力学理解。原位原子力显微镜可以直接探测驱动摩擦膜形成的二烷基二硫代磷酸锌添加剂(称为ZDDP基添加剂)的纳米级机械力化学，以及它们与新型基础油和共添加剂(包括钼基摩擦改进剂和分散剂)的相互作用。通过对摩擦膜生长动力学的测量和解释，可以确定抗磨添加剂和共添加剂之间的协同或拮抗作用。结合宾夕法尼亚大学的异地化学和结构表征技术，以及埃克森美孚的润滑油专业知识和成分规模测试，这项研究将有助于为下一代润滑油进行预测性设计、开发和实施先进配方。通过确定共添加剂如何影响摩擦膜生长的基本机理，从长远来看，这项研究将有助于确定无硫和无磷的抗磨添加剂。众所周知，硫和磷对汽车尾气排放有有害影响，因此开发ZDDP添加剂的替代品对于进一步减少汽车尾气排放至关重要。

Automobile engine oils typically include several different performance additives, each of which serves a crucial role in improving fuel efficiency and engine reliability. One of the additive types that are routinely added to such lubricants are anti-wear additives, which are required to reduce wear and failure when metal-on-metal contact occurs between the various parts within automobile engines. One such additive, a molecule based on a combination of zinc, sulfur, phosphorous, oxygen, and hydrocarbons, is so effective at reducing wear while being inexpensive to produce that it is used in nearly every automotive engine oil. This molecule works by forming surface films at certain contact points within the engine. These films serve as a protective cushion for the underlying metal parts, protecting them from wear. Despite its widespread use, it remains unclear how this molecule generates these protective films. Increasingly, automotive lubricants are being formulated with lower viscosities which help improve fuel economy and reduce undesirable emissions. Unfortunately, the molecules used to formulate these lower viscosity oils can interfere with the anti-wear molecule?s ability to generate protective films and provide adequate wear protection. This Grant Opportunities for Academic Liaison with Industry (GOALI) research aims to contribute to solving this problem by using novel nanotechnology methods to improve our understanding of how the anti-wear protective films are formed and how their formation is affected by interactions with other types of additives. Findings of this research will inform the design of next-generation automotive lubricants and will thus have a direct impact on the U.S. economy through improved energy saving, reductions in maintenance-related costs, and reduction of undesirable emissions.In this research, a quantitative kinetic and thermodynamic understanding of anti-wear tribofilm formation mechanisms will be formulated using novel in-situ atomic force microscopy methods, recently developed at UPenn. In-situ atomic force microscopy enables the direct probe of nanoscale mechanochemistry of zinc dialkyldithiophosphate additives (known as ZDDP-based additives) which drives formation of tribofilms, as well as their interactions with novel basestock and co-additives including molybdenum-based friction modifiers and dispersants. Synergism or antagonism between anti-wear additives and co-additive chemistries will be identified and understood through measurement and interpretation of tribofilm growth kinetics. Together with ex-situ chemical and structural characterization techniques at UPenn, as well as lubricant expertise and component-scale testing at ExxonMobil, this research will help enable predictive design, development, and implementation of advanced formulations for next-generation lubricants. By identifying how co-additives affect the fundamental mechanisms of tribofilm growth, this research will in the longer-term help identify sulfur and phosphorous-free anti-wear additives. Sulfur and phosphorous are known to have deleterious impacts on automotive emissions, and thus developing alternatives to ZDDP additives is crucial for further reducing automotive emissions.