Shear thickening under high shear using bimodal dispersions

半导体制造是美国在全球经济中保持竞争力的一项关键技术，尤其是在芯片短缺继续成为全球头条新闻的情况下。化学机械抛光（CMP）是一种关键的加工技术，被半导体工业用于制造各种各样的材料和器件，包括晶圆、逻辑器件、存储芯片和微电子机器（MEMs）。CMP工艺使用稳定颗粒的浓缩悬浮液，当以非常高的剪切速率抛光表面时，会产生磨损并去除废料。高剪切加工在其他制造操作中也至关重要，如涂层、喷涂和润滑流。先前对高剪切流变性（10,000 s-1）的研究有助于解释导致浓缩悬浮液粘度大幅增加的潜在机制，这通常被称为剪切增稠。本项目将使用一系列实验来表征由相对小颗粒和大颗粒混合物组成的悬浮液在大范围高剪切条件下的剪切增稠行为。寻找小颗粒和大颗粒在高剪切条件下相互作用以改变和在某些情况下消除剪切增厚的机制是一个重要的、基本的粒子科学问题。该项目的目标是充分详细地确定流动下颗粒混合物动力学的机制，以便将研究结果推广到其他颗粒系统和流动类型，包括抛光、管道和喷嘴流动。利用高剪切流变性结合散射实验来监测悬浮液中的结构形成，该项目有可能展示一种高剪切颗粒流的新机制，这种机制可能导致管道和喷嘴的堵塞以及抛光过程中缺陷的形成。最终，这项研究有可能影响广泛的行业，包括用于平板显示器和太阳能电池的大面积硅制造，纸张填料和涂层的均匀应用，焊接油墨、陶瓷、复合材料的改进加工，以及缓释药物配方的稳定。该项目将成为培养流变学以及颗粒和表面科学领域的研究生和本科生的基础。该项目还将为初中和高中教师提供获得动手实验经验的机会，并将研究成果转化为课堂教学。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Semiconductor manufacturing is an essential technology for US competitiveness in the global economy, especially as chip shortages continue to make headlines worldwide. Chemical Mechanical Polishing (CMP) is a critical processing technology that is used by the semiconductor industry to manufacture a wide variety of materials and devices, including wafers, logic devices, memory chips, and microelectronic machines (MEMs). The CMP process uses concentrated suspensions of stable particles that create abrasion and remove waste materials when polishing surfaces at very high shear rates. High shear processing is also critical in other manufacturing operations such as coating, spraying, and lubrication flows. Previous research in high shear rheology (10,000 s-1) has helped explain the underlying mechanisms leading to large increases in the viscosity of concentrated suspensions, which is commonly called shear thickening. This project will use a series of experiments to characterize the shear thickening behaviors of suspensions composed of mixtures of relatively small and large particles under a wide range of high shear conditions. Finding the mechanisms by which smaller and larger particles interact to modify and, in some cases, eliminate shear thickening under high shear conditions is an important, fundamental particle science problem. The goal of this project is to determine mechanisms underlying the dynamics of particle mixtures under flow in sufficient detail that findings can be generalized to other particle systems and flow types, including polishing, pipe, and nozzle flows. Using high shear rheology combined with scattering experiments to monitor structure formation in the suspension, the project has potential to demonstrate a new mechanism for high shear particle flow that can result in jamming of pipes and nozzles and the formation of defects in polishing. Ultimately, this research has potential to impact a wide range of industries, including large area silicon manufacturing for flat panel displays and solar cells, uniform application of paper filler and coatings, improved processing of soldering inks, ceramics, composites, and stabilization of time-release pharmaceutical formulations. The project will form the basis for training graduate and undergraduate students in the fields of rheology as well as particle and surface science. The project will also provide opportunities for middle and high school teachers to gain hands-on laboratory experience and to translate research to their classrooms.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.