Triboelectric charging of granular materials

1235908PI：桑卡拉当颗粒状物质流动时，颗粒相互摩擦，可能会带电。颗粒的带电会导致几个问题，例如扰乱流动，甚至引发爆炸。什么时候？摩擦充电？是科学中最著名的领域之一--当他们走过地毯时，当他们触摸门把手时，每个人都会注意到它，或者当他们在自己的头发上摩擦气球时，看到气球和头发是如何带电的--它的科学基础基本上是完全未知的。例如，尚不清楚表面之间转移的物种是电子、离子还是物质碎片。这个项目将通过开发关注基本问题的简单模型系统，采取合理的方法来理解颗粒材料中的摩擦电荷？这些模型系统包括具有特殊性质和特殊流动几何形状的颗粒材料，以及以受控几何形状摩擦的散装材料，以更简单地解决与颗粒系统相关的问题。我们的研究将包括三个方面：(1)特殊选择的颗粒和流型的颗粒流动实验，(2)作为颗粒材料多分散性效应模型的非对称摩擦实验，以及(3)与理论/模拟相比较的明确材料表面的实验。我们的实验将阐明几个关键问题，包括在充电过程中转移什么类型的物种(例如，电子、离子或物质)，颗粒材料的颗粒尺寸分布在电荷转移中的作用，以及湿度(即表面的水吸附)如何影响电荷转移。通过从基本的角度理解摩擦充电，我们的工作可能会帮助从事工业工作的科学家和工程师解决与这个普遍存在的问题相关的问题。

1235908PI: SankaranWhen granular materials flow, the particles rub against each other and can become electrostatically charged. The charging of particles causes several problems, such as disrupting the flow or even initiating explosions. While ?triboelectric charging? is one of the most well-known areas of science -- everyone notices it when they walk across a rug and get a shock as they touch a doorknob, or when they rub a balloon on their hair and see how the balloon and hair become charged -- its scientific basis is in essence completely unknown. For example, it is not clear whether the species transferred between surfaces are electrons, ions, or bits of material. This project will take a rational approach to understanding triboelectric charging in granular materials by developing simple model systems that focus on fundamental questions ? these model systems include granular materials with particular properties and special flow geometries, and bulk materials rubbed in controlled geometries to more simply address issues relevant to granular systems. Our investigation will consist of three thrusts: (1) particle flow experiments with specially chosen particles and flow patterns, (2) asymmetric rubbing experiments as a model for polydispersity effects in granular materials, and (3) experiments with well-defined material surfaces that can be compared with theory/simulation. Our experiments will elucidate several key questions, including what type of species (e.g., electron, ion, or bits of material) are transferred during the charging process, what is the role of the particle size distribution in the charging of granular materials, and how does humidity (i.e. water adsorption on surfaces) influence charge transfer. By understanding triboelectric charging from a fundamental perspective, our work may help scientists and engineers working in industry address problems related to this pervasive issue.