Rheology of Nanosize Powder Suspensions

该奖项是根据2009年美国复苏和再投资法案（公法111-5）资助的。高负载纳米级粉末悬浮液的流变行为提出了科学和技术挑战。当颗粒尺寸接近纳米级时，悬浮液的粘度急剧增加。当固体含量接近30 vol时，粘度变得难以处理。然而，我们最近发现单糖和双糖（即果糖和蔗糖）显著降低纳米氧化铝悬浮液的粘度。提出的研究的主要目的是了解高负载纳米级粉末悬浮液的流变行为，其中粒子势场重叠，因此絮凝成为一个严重的问题。另一个目标是了解低分子量（MW）糖在降低粘度方面的重要作用。我们将研究颗粒表面，水和糖分子之间的分子水平相互作用，以建立糖分子特性与悬浮液粘度之间的关系。这个项目的智力价值在于，在完成后，我们将能够描述纳米级粉末悬浮液在含水糖苷溶液中的流动行为，其中表面化学起着重要作用。具体来说，是应变率程控流变实验；低温差示扫描量热法；胶体探针原子力显微镜；变温1H、1H- 27al、13C核磁共振（NMR）波谱实验，作为固体组成和含量、糖类种类和浓度的函数。将颗粒间电位整合到粘度表达式中，并修改由于聚类和/或结合水造成的颗粒堆积，将使我们能够定量描述纳米粉末悬浮液的流动行为，以及用糖或类似添加剂控制粘度。更广泛的影响纳米粉末悬浮液在超薄电介质、固体氧化物燃料电池、膜、涂层、磨料抛光、粘合剂和防晒霜等领域都有应用。本研究的一个实际结果将是阐明粘度如何随固体含量及其表面化学变化，以及低分子量糖如何降低粘度。这项研究的结果将使我们能够控制许多纳米颗粒悬浮液的流动行为，并配制出高固体含量、低粘度的悬浮液，这些悬浮液具有纳米级的特征。因此，该项目对拥有数十亿美元收入的不同行业具有重大而广泛的影响。该项目将允许在纳米粉体加工科学的研究生教育。为此，将招收一名国内女学生。在过去十年中，大约40%的pi研究生是女性。此外，将通过新生导师计划和女性科学与工程计划招收来自代表性不足群体的本科生。多年来，他的研究小组平均每年聘用两名本科生。PI制作了一个教育视频“材料问题”，将在ASM国际全国范围内分发，以招收工程专业，特别是MSE专业的学生。PI还根据当前的研究主题制作了一个短视频剪辑：悬浮液的粘度：魔法还是科学。我们打算再次制作短视频片段，通过互联网在全国广泛传播。此外，在PI每年教授的陶瓷加工课程中，将开发并实施一个展示粘度随糖浓度变化的本科生实验室实验。使用零度以下DSC、变温核磁共振和复杂的胶体探针原子力显微镜实验直接测量粒子间力，将使其他领域的科学家能够在广泛的领域实施这些技术。

This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5) 0931038AkincIntellectual MeritThe rheological behavior of highly loaded, nanosize powder suspensions presents scientific and technological challenges. As the particle size approaches nanoscale, the viscosity of the suspension increases sharply. When the solids content approaches 30 vol, the viscosity becomes intractable. However, we recently discovered that mono and disaccharides (i.e. fructose and sucrose) dramatically decrease the viscosity of nano alumina suspensions. The primary objective of the proposed research is to understand the rheological behavior of highly loaded nanosize powder suspensions where particle potential fields overlap, thus flocculation becomes a serious concern. An additional objective is to understand the dramatic role low molecular weight (MW) saccharides play in reducing the viscosity. We will investigate the molecular level interactions between particle surface, water, and saccharide molecules to establish a relationship between characteristics of saccharide molecule and the viscosity of the suspension. The intellectual merit of this project lies in the fact that, upon completion, we will be able to describe the flow behavior of nanosize powder suspensions in aqueous sachharide solution where surface chemistry plays a significant role. Specifically, experiments with strain rate programmed rheometry; sub zero temperature differential scanning calorimetry (SZT-DSC); colloidal probe atomic force microscopy (CP-AFM); and variable temperature 1H, 1H-27Al, and 13C nuclear magnetic resonance (NMR) spectroscopy experiments will be carried out as functions of solids composition and content, saccharide type and concentration. Integrating interparticle potential to the viscosity expression and modifying the particle packing due to clustering and/or bound water will allow us to quantitatively describe flow behavior of nano powder suspensions and control of viscosity with saccharide or similar additives.Broader ImpactNano owder suspensions find applications in ultra thin dielectrics, solid oxide fuel cells, membranes, coatings, abrasive polishing, adhesives, and sunscreens, among others. A practical consequence of this research will be the elucidation of how the viscosity varies with the solids content and its surface chemistry, and how low MW saccharides reduce the viscosity. The results from this research will enable us to control the flow behavior of many nanoparticle suspensions, and formulate high solids content, low viscosity suspensions that are consolidated to components with features in the nanoscale. Therefore, this project has significant broader impacts on diverse industries that have multi billion dollar revenues. This project will allow education of a graduate student in the nanosize powder processing science. For this, a domestic female student will be recruited. Approximately 40% of PIs grad students in the last decade were female. In addition, undergraduate students preferably from underrepresented groups will be recruited through Freshman Mentor Program and the Program for Women in Science and Engineering. Over the years, the PI has employed, on the average, two undergraduate students per year in his research group. The PI has produced an educational video Materials Matter to be distributed ASM International across the country to recruit students to engineering, in particular MSE. PI has also developed a short video clip based on the current research topic: Viscosity of Suspensions: Magic or Science. We intend to make short video clip again to be distributed broadly across the country via internet. Also an undergraduate laboratory experiment demonstrating the variation of viscosity with saccharide concentration will be developed and implemented in Ceramic Processing course that the PI teaches every year. Use of sub zero temperature DSC, variable temperature NMR, and sophisticated colloidal probe AFM experiments for measuring interparticle forces directly will allow scientists in other fields to implement these techniques in broad range of fields,