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

CBET-0828905Osuji该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3年计划。许多努力致力于了解颗粒负载流体的流动行为，这些材料在工业中的潜在普遍性是一个强大的动力。最近在胶态体系中对剪切增稠现象的观察，为从根本上理解这类重要材料的流变学提供了一个机会。科学objectivesThe建议的工作是针对回答关键问题，所观察到的剪切增稠，并探讨几个定性的新现象所显示的剪切增稠凝胶。 该提案描述了一个详细的计划（1）在这些材料中的剪切增稠的表征，（2）在稳态的内应力动力学的研究和（3）有序的各向异性微观结构的演化的研究剪切变形的这种胶体凝胶。学术价值排斥和硬球体系中的剪切稠化已引起人们的极大关注。相比之下，在构成大多数工业应用的聚合物体系中，剪切增稠既没有被预测也没有被探索。拟议的研究解决了这一差距，并将阐明有吸引力的系统中的剪切增稠的起源，以及相互作用强度和体积分数的依赖。它将构成第一个定量研究的短期和长期的时间尺度动态应力，导致系统淬火从液体到凝胶状态的软材料。最后，它将提供一个新的面貌，无与伦比的细节，在形成各向异性涡排列聚集体在一个复杂的流体下流动。更广泛的影响。技术影响烟雾颗粒是一种商品材料，销售量以百万吨计，应用于各种配方和产品。正是由于这个原因，填充牛顿流体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很常见。PI与Cabot公司保持着联系，他们的工作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。还与工业界就流变仪的设计和操作进行技术交流。教育和外联PI是一个新的教员与教育和外联的浓厚兴趣。该项目将积极寻求代表性不足的群体参与三个本科生研究项目。研究生将获得复杂流体的广泛实验背景，并通过教学，本科生导师和当地外展活动参与教育。 作为耶鲁大学复杂流体/软材料研究的更广泛推动力的一部分，PI将开发课程，将项目主题纳入复杂流体流变学模块。结果将在一个互动网站上公布，并将定期在区域新英格兰复杂流体工作组（NECF）的季度会议以及国家会议上公布。

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.