GOALI Collaborative Research: Engineering magnetorheological fluids by controlling nonmagnetic particle interactions

0932680/0932715 Klingenberg/Zauscher磁流变（MR）流体是可磁化颗粒的悬浮液，其流变性质可以通过施加的磁场显著且可逆地改变。这些材料可用于各种应用中，目前的注意力主要集中在汽车设备（例如，主动阻尼系统和离合器）。应用程序可以提高车辆质量（例如，驾驶和操纵）以及改善车辆的汽油里程。过去的研究表明，磁流变液的场致行为可以很大程度上解释为静磁力及其与流体动力的竞争。然而，MR流体的应用需要其它性质的某些装置相关特性，诸如关闭状态粘度、沉降、再分散性和耐久性。这些性质强烈地受到除磁力之外的粒子间力的影响。因此，很明显，设计用于装置的MR流体需要理解各种颗粒间力与悬浮液的宏观性质之间的关系。 在拟议的工作中，我们将使用几种互补的方法来探索粒子间力和宏观行为之间的关系，并研究观察到的行为的机制。 铁表面间的非磁力将通过在表面接枝各种物质而改变。接枝层对颗粒间力的影响将使用胶体探针显微镜直接测定，其中法向和侧向（即，摩擦力）将被测量。接枝层对宏观流变性能的影响也将通过实验确定。最后，我们将使用粒子级模拟来研究粒子间力的变化如何影响宏观行为。 这将使我们能够确定在表面上接枝物种引起的测量颗粒间力中观察到的变化是否可以解释所观察到的宏观性质的变化。拟议的研究将提供有关MR流体性质的新信息，并提高我们优化流体和各种应用所需颗粒涂层的能力。这项工作也将更普遍地提高我们对颗粒凝胶的理解，因为我们将研究具有更深吸引力的井深的系统，具有更大颗粒的系统，并探测比通常研究更大的变形流变特性。该项目的资金将用于支持研究生，他们将在新兴的磁流变学领域接受培训，以及胶体探针显微镜和胶体凝胶和悬浮液流变学的更一般领域。学生们还将通过与通用汽车公司的互动接触到他们工作的工业应用。我们的小组每年也让本科生参与研究，因此我们也将在整个项目过程中培训MR，悬浮液流变学和胶体科学方面的本科生。 私人研究员参与了其他教育项目，这些项目将从拟议的工作中受益。Klingenberg共同教授大一课程“社会导论”是工程大挑战，它探讨了社会如何是重大的挑战将需要工程师来解决它们。本课程的目标是招收新的学生进入工程，并招聘和留住更大比例的妇女。社会的主要挑战之一是能源可持续性。MR技术的许多应用都是出于车辆的能源经济性，因此被纳入了大挑战课程，以说明当前的研究活动如何应对社会挑战。在过去的6年里，Zauscher参与了一个REU项目，该项目为Gallaudet大学的听障学生提供实验室体验。 我们建议每年夏天聘请一名这样的学生进行CPM测量。

0932680/0932715Klingenberg/ZauscherMagnetorheological (MR) fluids are suspensions of magnetizable particles, whose rheological properties can be dramatically and reversibly altered by applied magnetic fields. These materials can be exploited in a variety of applications, with much of the current attention focused on automotive devices (e.g., active damping systems and clutches). Applications can improve vehicle quality (e.g., ride and handling) as well as improve the gas mileage of vehicles. Past research has illustrated that the field induced behavior of MR fluids can be explained largely in terms of magnetostatic forces and their competition with hydrodynamic forces. However, applications of MR fluids demand certain device dependent characteristics of other properties, such as off state viscosity, sedimentation, redispersability, and durability. These properties are strongly influenced by interparticle forces other than magnetic forces. It is thus apparent that designing MR fluids for devices requires an understanding of the relationships between various interparticle forces and macroscopic properties of the suspensions. In the proposed work, we will use several complementary approaches to probe the relationships between interparticle forces and macroscopic behavior, and to investigate the mechanisms for observed behavior. Nonmagnetic forces between iron surfaces will be altered by grafting various species to the surfaces. The impact of the grafted layers on interparticle forces will be determined directly using colloidal probe microscopy, in which both the normal and lateral (i.e., friction) will be measured. The effects of the grafted layers on the macroscopic rheological properties will also be determined experimentally. Finally, we will use particle level simulations to examine how changes in interparticle forces affect macroscopic behavior. This will allow us to determine if changes observed in the measured interparticle forces caused by grafting species on the surfaces can account for the observed changes in macroscopic properties.Intellectual merit. The proposed research will provide new information about the properties of MR fluids, and improve our ability to optimize fluids and requisite particle coatings for various applications. This work will also more generally improve our understanding of particulate gels, as we will be investigating systems with deeper attractive well depths, systems with larger particles, and probing larger deformation rheological properties than typically studied.Broader impact. Funding for this project will be used to support graduate students, who will be trained in the emerging field of magnetorheology, as well as colloidal probe microscopy and the more general fields of colloidal gels and suspension rheology. The students will also be exposed to industrial applications of their work through interactions with General Motors. Our groups also involve undergraduate students in research every year, and thus we will also be training a stream of undergraduates in aspects of MR, suspension rheology, and colloid science throughout the course of this project. The PIs are involved in other education projects that will benefit from the proposed work. Klingenberg co teaches the freshman course "Introduction to Society" is Engineering Grand Challenges, which examines how society is significant challenges will require engineers to solve them. The goals of this course are to recruit new students into engineering, and to recruit and retain a larger fraction of women. One of society's main challenges is energy sustainability. Numerous applications of MR technology are motivated by energy economy in vehicles, and thus are incorporated into the Grand Challenges course to illustrate how current research activities are addressing society's challenges. Zauscher has been involved over the last 6 years in an REU program that provides laboratory experiences for hearing impaired students from Gallaudet University. We propose to engage one such student each summer in the CPM measurements.