GOALI - The Effects of Triboelectrification on Granular Flow, Mixing and Segregation

一磅普通小麦粉的爆炸力几乎是TNT的两倍。要利用这种能量，只需要将面粉颗粒悬浮起来，并暴露在火花中。因此，工业花费大量的努力来控制粉末中的静电充电。尽管有这些预防措施，静电放电还是会引起致命的粉尘爆炸。不那么引人注目的是，粒子的静电充电在工业上得到了广泛的应用，例如传统的印刷、电镀膜和过滤，以及更现代的应用，如晶体自组装。电气化在天然颗粒系统中也普遍存在，它影响着风沙的输送和地质沉积模式。令人惊讶的是，经过几个世纪的研究，固体带电的一些最基本的性质无法解释。举个简单的例子，任何在冬天把鞋子蹭到尼龙地毯上而受到电击的人都可以证明，缺乏自由载流子的绝缘体比导体更容易转移电荷。这种效应已被广泛研究，并证明与导体携带电荷到地面的能力无关。知识价值：颗粒电气化的重要性在制药开发中最为迫切。这方面最著名的例子可能是药物的气溶胶输送，既用于肺部治疗（如哮喘），也用于输送不能在消化道中存活的药物（如胰岛素），或者不适合其他剂型的药物（如水溶性低的药物，或太大而不能经皮扩散的大分子）。雾化主要依赖于控制颗粒电荷，以防止聚集和促进输送到深肺。鲜为人知的是，最近有研究表明，困扰颗粒加工的许多流动和混合并发症可直接归因于静电充电。这种复杂性包括机械上难以区分的材料的自发分离，以及颗粒聚集成复杂的团簇，这些团簇可以根据微妙的实验细节交替地阻碍或增强颗粒流动。直到最近，还没有一个主要的研究项目处理这些基本的，但实际上很重要的问题：工业上，它们是在排除故障的基础上解决的，很少有长期的学习，从根本上说，它们的根本原因被忽视了。这一建议的目的是推进颗粒行为的理解在静电荷的存在。这项工作的主要部分将是产生实验验证的计算工具。这将改善现有的工业颗粒工艺，这些工艺因难以理解混合和流动困难而臭名昭著，并将对非常基本但看似复杂的颗粒行为产生新的见解。将用于实现这一目标的方法结合了一般适用的几何形状的重点实验，以及带电颗粒流动、混合、偏析和聚集的直接计算模拟的发展。更广泛的影响：人们不需要费力就能发现这项研究的广泛含义。在工业方面，其影响是显而易见的：在制药行业，除了气溶胶应用之外，整个生产工厂和生产线经常因为颗粒流动和混合控制失败而关闭，更好地了解颗粒静电将提高这些过程的可靠性。在更远的地方，地球物理学中有一个长期存在的、尚未解决的悖论，即沙尘暴中的沙粒产生了很大的电荷梯度，尽管它们与其他沙粒几乎没有摩擦。尽管现场和实验室都进行了调查，但这些梯度的来源仍然难以捉摸，因为它们依赖于对带电粒子之间的动力学知之甚少。最近还提出了将颗粒电荷与火星地貌联系起来的机制。颗粒静电还将影响新技术，包括用于高能锂电池和新型半导体器件等应用的纳米复合材料。这些应用涉及制备、加工和混合具有高电荷晶体习性的颗粒，并将受益于本提议将带来的对带电粒子行为的基础科学和应用科学的改进理解。本提案中的研究将与教育和推广活动相结合，包括研究生、本科生和高中粒子技术研究培训。此外，罗格斯大学的PI将继续以招募女性和少数族裔为目标。

CBET-0827404ShinbrotPound for pound, common wheat flour contains nearly twice the explosive power of TNT. To harness this power requires only that flour particles be suspended and exposed to a spark. Consequently, industries expend significant efforts to control static charging in powders. Despite these precautions, static discharges regularly cause fatal dust explosions. Less dramatically, electrostatic charging of particles is widely applied industrially, for example in conventional printing5, electrocoating6, and filtration, as well as in more modern applications such as crystal self-assembly. Electrification is ubiquitous in natural granular systems as well, where it influences Aeolian sand transport9 and geological sedimentation patterning. Surprisingly, after centuries of study, some of the most basic properties of electrification of solids defy explanation. As one brief example, anyone who has received a shock after scuffing their shoes on a nylon rug in wintertime can attest that insulators, which lack free charge carriers, transfer charge more readily than conductors. This effect has been extensively studied and proven to be independent of the ability of conductors to carry charges to ground.Intellectual Merit: Nowhere is the importance of granular electrification more pressing than in pharmaceutical development. Probably the best known example of this is in the aerosol delivery of pharmaceuticals, used both for pulmonary therapeutics (as in asthma) and to deliver drugs that either will not survive in the digestive tract (e.g. insulin) or are otherwise unsuitable for other dosage forms (e.g. agents with low water solubility, or macromolecules that are too large to diffuse transdermally). Aerosolization depends critically on control of particle charging to prevent aggregation and to promote delivery to the deep lung. Less widely known, it has recently been demonstrated that many of the flow and mixing complications that plague granular processing are directly attributable to electrostatic charging. Such complications include spontaneous segregation of mechanically indistinguishable materials, and aggregation of grains into complex clusters that can alternatively impede or augment a granular flow depending on subtle experimental details. Until recently, no major research program has dealt with these basic, yet practically important, problems: industrially, they are addressed on a trouble-shooting basis where little is learned for the long term, and fundamentally, their root causes are ignored. The objective of this proposal is to advance the understanding of granular behaviors in the presence of static charging. A major part of this work will be to produce experimentally validated computational tools. This will improve existing industrial granular processes that are notorious for poorly understood mixing and flow difficulties, and will produce new insights into very basic, yet deceptively complex, granular behaviors. The methods that will be used to achieve this objective combine focused experiments in generally applicable geometries side-by-side with the development of direct computational simulations of flow, mixing, segregation, and aggregation of charged grains. Broader Impacts: One does not need to look hard to find broad implications of this research. On the industrial side, the implications are clearcut: in the pharmaceutical industry, beyond aerosol applications, entire production plants and product lines are not infrequently shut down due to failures to control granular flow and mixing, and better understanding of granular electrostatics will improve the reliability of these processes. Further afield, there is a longstanding, unresolved paradox in geophysics that grains in sandstorms generate large charge gradients although they have little beyond other sand grains to rub against. Despite both field and laboratory investigations, the sources of these gradients remain elusive as they depend on poorly understood dynamics between charged particles. Mechanisms have also recently been proposed to link granular charging to Martian landforms. Granular electrostatics also will impact new technologies, including nanocomposites under development for applications such as high energy Lithium batteries, and novel semiconductor devices. These applications involve the preparation, processing and mixing of grains with highly charged crystal habits, and will benefit from the improved understanding of both the basic and the applied sciences of charged particle behaviors that this proposal will bring. The research in this proposal will be integrated with educational and outreach initiatives including graduate, undergraduate and high school research training in particle technology. In addition, the Rutgers PI's will continue to target the recruitment of women and minorities.