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

CBET-0827404 ShinbrotPound按磅计算，普通小麦粉含有的爆炸力几乎是TNT的两倍。要利用这种力量，只需将面粉颗粒悬浮并暴露在火花中即可。因此，各行各业都在努力控制粉末中的静电。尽管采取了这些预防措施，静电放电经常会导致致命的粉尘爆炸。不那么引人注目的是，颗粒的静电荷电在工业上得到了广泛的应用，例如，在传统的印刷、电镀和过滤中，以及在更现代的应用中，如晶体自组装。带电现象在天然颗粒系统中也是普遍存在的，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。举一个简单的例子，任何人在冬天将鞋子在尼龙地毯上擦伤后受到电击，都可以证明，没有自由电荷载体的绝缘体比导体更容易转移电荷。这种效应已被广泛研究，并被证明与导体将电荷带到地面的能力无关。智力上的优点：在制药开发中，颗粒带电的重要性是最紧迫的。这方面最著名的例子可能是气雾剂给药，既用于肺部治疗(如哮喘)，也用于输送不能在消化道存活的药物(如胰岛素)或不适合其他剂型的药物(如低水溶性药物，或大分子太大而不能经皮扩散)。气雾化严重依赖于控制颗粒荷电，以防止聚集并促进向肺深部的输送。不那么广为人知的是，最近有证据表明，困扰颗粒加工的许多流动和混合并发症直接可归因于静电充电。这些复杂情况包括机械上难以区分的物质的自发分离，以及颗粒聚集成复杂的团簇，根据微妙的实验细节，这种聚集可能会阻碍或增强颗粒流。直到最近，还没有一个主要的研究项目处理这些基本但实际重要的问题：在工业上，这些问题是以故障排除为基础来解决的，长期几乎没有学到什么，而且从根本上说，它们的根本原因被忽视了。这一建议的目的是促进对静电存在下的颗粒行为的理解。这项工作的主要部分将是生产经过实验验证的计算工具。这将改善现有的工业颗粒过程，这些过程以混合和流动困难而臭名昭著，并将对非常基本但具有欺骗性的复杂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在普遍适用的几何中的集中实验和对带电颗粒的流动、混合、分离和聚集的直接计算模拟的发展。更广泛的影响：人们不需要努力寻找这项研究的广泛影响。在工业方面，其影响是明确的：在制药行业，除了气雾剂应用之外，整个生产线和生产线都不会因为控制颗粒流动和混合失败而频繁关闭，而更好地了解颗粒静电将提高这些工艺的可靠性。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，即沙尘暴中的颗粒会产生很大的电荷梯度，尽管除了其他沙粒之外，它们几乎没有什么可摩擦的。尽管进行了野外和实验室的研究，但这些梯度的来源仍然难以捉摸，因为它们依赖于人们对带电粒子之间的动力学知之甚少。最近还提出了将颗粒充电与火星地貌联系起来的机制。颗粒静电也将影响新技术，包括正在开发的纳米复合材料，用于高能锂电池和新型半导体器件。这些应用涉及具有高带电晶体习惯的颗粒的制备、加工和混合，并将受益于对这一提议将带来的带电粒子行为的基础科学和应用科学的更好理解。这项提案中的研究将与教育和推广活动相结合，包括研究生、本科生和高中的粒子技术研究培训。此外，罗格斯国际将继续以招募妇女和少数族裔为目标。

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.