Structure Formation, Rheology and Internal Stress Dynamics in Shear Thickening Attractive Colloidal System

CBET-0828905Osuji本提案概述了以复杂流体流变学为中心的综合研究、教学和推广的三年计划。人们一直致力于了解颗粒流体的流动行为，而这些材料在工业中的普遍存在是一个强大的推动力。最近在凝胶形成胶体体系中观察到的剪切增稠现象，为从根本上理解这类重要物质的流变学提供了一个机会。a.科学目的这项拟议的工作旨在回答有关所观察到的剪切增稠的关键问题，并探索剪切增稠凝胶所显示的几种新的定性现象。这项建议描述了一个详细的计划：(1)这些材料中剪切增稠的表征，(2)定态内应力动力学的研究，以及(3)有序各向异性微结构对这种胶体凝胶剪切变形的演化的研究。相比之下，在构成大多数工业应用的絮凝系统中，剪切增稠既没有被预测，也没有被探索。这项拟议的研究解决了这一差距，并将阐明吸引系统中剪切增厚的起源以及对相互作用强度和体积分数的依赖。这将构成对软材料中从液体到凝胶态的系统淬火导致的短和长时间尺度的应力动态的第一个定量研究。最后，它将以无与伦比的细节提供一个新的视角，研究流动中复杂流体中各向异性涡度排列的聚集体的形成。技术影响烟熏颗粒是商品材料，销售额以数百万吨计，在各种配方和产品中都有应用。正因为如此，充满牛顿和粘弹性流体的流变学是一个活跃的研究领域，工业界和学术界之间的科学交流是常见的。PI与卡博特公司保持联系，他们的人员经常参加当地复杂流体社区的会议，促进进一步的互动。此外，还与业界就流变仪的设计和操作进行了技术交流。教育和外展PI是一名对教育和外展有着浓厚兴趣的新教员。该项目将积极寻求代表不足的群体参与三个本科生研究项目。研究生将获得广泛的复杂流体实验背景，并通过教学、本科生指导和当地外展活动参与教育。作为耶鲁大学更广泛的复杂流体/软材料研究的一部分，PI将在复杂流体流变学模块中开发结合该项目主题的课程。结果将在一个互动网站上公布，并将定期在新英格兰地区复杂流体工作组(NECF)的季度会议上以及全国会议上公布。

CBET-0828905OsujiThis proposal outlines a 3-year plan of integrated research, teaching and outreach centered on complex fluid rheology. Much effort has been devoted to understanding the flow behavior of particulate laden fluids, with the underlying ubiquity of these materials in industry a strong motivator. The recent observation of shear thickening in gel forming colloidal systems presents an opportunity to contribute to the fundamental understanding of the rheology of this important class of materials.A. Scientific objectivesThe proposed work is directed towards answering key questions regarding the observed shear thickening, and to exploring several qualitatively new phenomena displayed by shear thickened gels. This proposal describes a detailed plan for (1) the characterization of shear thickening in these materials, (2) the study of internal stress dynamics in stationary states and (3) the study of the evolution of ordered anisotropic microstructures on shear deformation of such colloidal gels.B. Intellectual meritSignificant attention has been given to shear thickening in repulsive and hard sphere systems. By contrast, in flocculating systems, which constitute the majority of industrial applications, shear thickening has neither been predicted nor explored. The proposed study addresses this gap and will elucidate the origin of shear thickening in attractive systems as well as the dependence on interaction strength and volume fraction. It will constitute the first quantitative study of short and long timescale dynamics of stresses that result on system quenches from the liquid to the gel state in soft materials. Finally, it will provide a new look, with unparalleled detail, at the formation of anisotropic vorticity-aligned aggregates in a complex fluid under flow.C. Broader impact1. Technical impactFumed particles are commodity materials with sales measured in millions of tonnes and applications in all manner of formulations and products. The rheology of filled Newtonian and viscoelastic fluids is an active research area for exactly this reason, and scientific exchange between industry and academia is common. The PI maintains a relationship with Cabot Corp., and their personnel often attend meetings of the local complex fluids community, facilitating further interactions. There are also technical exchanges with industry concerning rheometer design and operation.2. Education and OutreachThe PI is a new faculty member with a strong interest in education and outreach. This project will actively seek the participation of underrepresented groups for three undergraduate research projects. Graduate students will gain a broad experimental background in complex fluids and be involved in education through teaching, mentorships of undergraduates and local outreach events. As part of a broader thrust in complex fluids/soft materials research at Yale, the PI will develop coursework incorporating themes from the project in a module on complex fluid rheology. Results will be published on an interactive website and will be regularly presented at the quarterly meetings of the regional New England Complex Fluids Workgroup (NECF) as well as at national meetings.