Using confocal rheometry to investigate shear thickening suspensions

使用共焦流变测量法研究剪切增稠悬浮液

• 批准号: 1232666
• 负责人: Itai Cohen
• 金额: $ 33.63万
• 依托单位: Cornell University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2012
• 资助国家: 美国
• 起止时间: 2012-07-15 至 2015-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1232666&HistoricalAwards=false
• 关键词: Using; confocal; rheometry; investigate; shear

1232666PI: CohenThe viscosity of colloidal suspensions can vary by orders of magnitude with shear rate. Such non-Newtonian behavior arises from the arrangement of suspended particles and their mutual interactions. Although numerical simulations and scattering experiments revealed much about the local and average suspension structures, particle dynamics at mesoscopic length scales, where non-Newtonian behaviors are believed to originate, are still poorly understood. This research program will continue to develop techniques that combine fast confocal microscopy with simultaneous rheological measurements to determine how changes in suspension mesoscopic structure alter the suspension viscosity. The current work will focus on three themes associated with shear thickening suspensions. First, we will determine how hydrocluster size distribution alters shear thickening in different size gaps. This task will be achieved by directly visualizing hydroclusters at various shear rates and investigating their behavior under confinement. Second we will determine how particle shape enhances shear thickening. Dimer and cubic particles will be used to investigate how shape anisotropy affects thickening. Finally we will investigate whether mechanisms for thickening at high volume fractions are hydrodynamic in origin or if, as many groups claim, at high volume fractions frictional contact forces come into play. These confocal rheometry techniques illustrate a new approach for determining the microscopic dynamics of non-Newtonian suspensions. Ultimately, research carried out in this project will enable design of shear thickening fluids. Such studies will have substantial ramifications due to the important role that shear thickening materials play in industrial applications. These fluids can be found in materials ranging from paints, to pastes, and even shear thickening drilling mud proposed for ?top kill? procedures (such as those used to control the ?blowout? of the Macondo well). Their handling is substantially complicated by their non-Newtonian behavior during processing and packaging. Thus, the goal of designing flow environments and fluids that when appropriate prevent or precipitate rapid changes in suspension rheology will have substantial impact on common industrial practices.A number of Education and outreach activities will be carried out. The PI is involved in creating performance based presentations on emergent phenomena in science. In addition to this activity, the PI will continue to organize the semiannual New York Complex Matter Workshops. These meetings are aimed at stimulating interaction among soft matter and statistical physics researchers from Syracuse, Cornell, RIT, General Electric, Kodak, Corning and other institutions and industrial labs in the area. The workshops will serve as an excellent opportunity for introducing graduate students and postdocs to the local academic and industrial research community.

胶体悬浮液的粘度随剪切速率的变化可以有数量级的变化。这种非牛顿的行为源于悬浮粒子的排列和它们之间的相互作用。尽管数值模拟和散射实验揭示了许多关于局部和平均悬浮结构的信息，但在介观长度尺度上的粒子动力学，即非牛顿行为的起源，仍然知之甚少。该研究项目将继续开发将快速共聚焦显微镜与同步流变测量相结合的技术，以确定悬浮液介观结构的变化如何改变悬浮液的粘度。目前的工作将集中在与剪切增厚悬浮液相关的三个主题上。首先，我们将确定氢簇大小分布如何在不同大小的间隙中改变剪切增厚。这项任务将通过在不同剪切速率下直接可视化氢团簇并研究它们在约束下的行为来实现。其次，我们将确定颗粒形状如何增强剪切增厚。二聚体和立方粒子将被用来研究形状各向异性如何影响增厚。最后，我们将研究在高体积分数下增稠的机制是否源于水动力，或者是否如许多小组所声称的那样，在高体积分数下摩擦接触力起作用。这些共聚焦流变学技术说明了一种确定非牛顿悬浮液微观动力学的新方法。最终，本项目的研究将为剪切增稠流体的设计提供依据。由于剪切增厚材料在工业应用中的重要作用，这些研究将产生实质性的影响。这些流体可以在各种材料中找到，从油漆到糊状物，甚至是用于？封顶?程序（如用于控制井喷）马孔多井的情况)。在加工和包装过程中，它们的非牛顿行为使它们的处理变得非常复杂。因此，设计流动环境和流体的目标，在适当的时候防止或沉淀悬浮液流变学的快速变化，将对常见的工业实践产生重大影响。将开展一些教育和外联活动。PI参与创建基于科学中突发现象的表演演示。除了这项活动外，PI还将继续组织半年一次的纽约复杂问题研讨会。这些会议旨在刺激来自锡拉丘兹、康奈尔、RIT、通用电气、柯达、康宁和该地区其他机构和工业实验室的软物质和统计物理研究人员之间的互动。研讨会将成为向当地学术和工业研究界介绍研究生和博士后的绝佳机会。