Triboelectric charging in granular systems

本项目主要研究化学性质相同材料的绝缘颗粒系统中的摩擦电荷。拟议的研究将进行与理论密切相关的实验，以解决这些系统中发生的电荷的性质，并将电荷与颗粒大小分布等影响联系起来。知识价值。当两个表面摩擦时发生的静电充电（“摩擦充电”）是物理学中最著名的现象之一。因此，对这一现象没有明确的科学解释是非常令人惊讶的。由化学性质相同的颗粒组成的颗粒系统的摩擦电荷特别令人困惑。而在不同类型粒子的混合物中，从一种粒子到另一种粒子的净电荷转移可以归因于材料性质的差异，当所有粒子具有相同的组成时，材料性质没有这种差异，然而，当粒子是绝缘体时，这些系统已知会经历大量的充电。此外，当所有颗粒由相同的材料组成时，实验表明，较小的颗粒带负电荷，较大的颗粒带正电荷。为什么粒子电荷的极性依赖于粒子的大小，以及为什么当所有粒子都由相同的材料组成时，会发生电荷，这些都很难理解。本研究将从两个方面阐明这些系统的充电行为和机理：1)我们将开展实验，定量表征粒度对化学性质相同的颗粒材料摩擦电荷的影响；2)我们将开展专门设计的实验，以检验摩擦电荷机制的假设，包括碰撞诱导的电子转移产生电子积累的非平衡动力学。我们的实验方法具有独特的能力，可以在受控环境中研究摩擦电荷，并且仅从颗粒相互作用中研究摩擦电荷，从而消除湿度和其他污染物（即容器或反应器壁）的影响。所提出的工作结果将有助于对化学相同颗粒系统中电荷转移的驱动力和机制的基本理解。更广泛的影响。这个项目的一个特别重点是大力指导本科生研究人员，包括妇女和代表性不足的少数群体成员。这些pi在这方面有着出色的记录，他们的团队中有大量本科生在期刊上发表论文，并继续攻读化学工程的博士学位。该项目还可以通过提高对摩擦充电的理解来造福社会。摩擦电荷发生在广泛的环境中，并且可能对包括安全在内的一系列问题产生影响（例如，摩擦电荷可能引起粉尘爆炸）。

0852772SankaranThis project is focused on studying triboelectric charging in insulating granular systems of chemically identical materials. The proposed research will carry out experiments closely aligned with theory to resolve the nature of the charging that occurs in these systems and relate the charging to such effects as particle size distribution. Intellectual merit. The electrostatic charging that occurs when two surfaces rub ("triboelectric charging") is one of the most well known phenomena in physics. It is thus very surprising that there is no clear scientific explanation for this phenomenon. The triboelectric charging of granular systems of chemically identical particles is particularly perplexing. While in mixtures with different types of particles, net charge transfer from one type of particle to the other can be attributed to a difference in the material properties, there is no such difference in material properties when all particles have the same composition, and yet these systems are known to undergo substantial charging when the particles are insulators. Furthermore, when all particles are composed of the same material, experiments show that smaller particles charge negatively and larger particles charge positively. Why there is a particle size dependence of the polarity of particle charge, and why charging occurs at all when all particles are composed of the same material is poorly understood. The proposed research will elucidate the charging behavior and mechanism in these systems through two thrusts: 1) we will carry out experiments to quantitatively characterize the effect of particle size on the triboelectric charging of chemically identical granular materials, 2) we will carry out experiments specifically designed to test the hypothesis for the mechanism of triboelectric charging including non equilibrium dynamics in which collision-induced electron transfer generates electron accumulation. Our experimental methodology is uniquely capable of studying triboelectric charging in a controlled environment and solely from particle particle interactions, removing the effect of humidity and other contaminants (i.e. container or reactor wall). The results of the proposed work will aid in a fundamental understanding of the driving force and mechanism for charge transfer in chemically identical granular systems. Broader impacts. A particular emphasis of this project is a strong effort to mentor undergraduate student researchers, including women and members of underrepresented minority groups. The PIs have excellent records in this regard, with a large number of undergraduate students in their groups publishing papers in refereed journals and proceeding to Ph.D. programs in chemical engineering. The project can also benefit society by enhancing the understanding of triboelectric charging. Triboelectric charging occurs in a wide range of contexts, and can have implications on a range of issues including safety (e.g., dust explosions can by cause by triboelectrical charging).