Pulsed Corona Discharge in Supercritical Carbon Dioxide: Fundamentals and Applications

摘要cps -0522578， PI: Lawrence A. Kennedy，伊利诺伊大学芝加哥分校，超临界二氧化碳脉冲电晕放电：基本原理与应用在努力增加激发态或反应物的密度，或处理非气体介质时，非热放电到高压、液体和多相系统的缩放是非常有趣的。超临界流体（SCFs）是一类特殊的高密度流体，由于其独特的清洁和溶剂化特性，在其自身的rite中进行了研究。SCFs的密度和输运性质介于气体和液体状态之间，具有固有的空间不均匀性，通常被称为“簇状”流体。该项目研究了几乎未开发但实际上很重要的SCF等离子体和放电领域。由于SCFs固有的簇状流体特性，预计在SCFs中持续存在的等离子体将具有独特的化学反应性；以及等离子体中通过电子冲击过程产生的自由基和离子。甚至SCF等离子体最基本的特性在很大程度上也没有被描述；所以我们利用它们独特属性的能力受到了严重阻碍。该项目的目标是研究和表征SCF等离子体中的放电起始和传播。在超临界压力和温度的大范围内进行了超临界CO2放电起始的实验研究。研究了流光击穿机理，包括临界电场、传播速度、直径、分支和火花跃迁。重点放在空间不均匀性的作用，导致固有的纳米级聚类等离子体的性质。诊断包括空间和时间分辨ICCD成像、光谱学和纹影技术。关于SCF中放电和流参数的综合数据库，包括击穿电压、流速度和SCF等离子体的空间特性，正在开始组装。更广泛的影响涉及科学、技术和教育的进步。这项研究为流在包含不同大小和结构的簇的非均匀介质中的传播提供了基本的新见解。因此，这项工作为其他人开发这种新型SCF等离子体提供了基础，这将补充高压气体和液体放电的研究。该研究还促进了尘埃等离子体和微等离子体相关领域的知识。从实用的角度来看，本研究为非热超临界等离子体的技术效益开辟了新的领域。利用SCF等离子体的特性可能会扩展和改进目前利用传统SCF的技术。非平衡等离子体和SCFs都被证明是氧化、蚀刻零件、去除污染、材料合成、传感器、细菌灭活和聚合的特殊工艺。这两个过程的结合有望带来显著的协同增强。研究和教育通过服务于几个重要群体的机制进行整合，包括：研究生和本科生以及通过开辟等离子体科学和工程的新领域的研究人员。本科生通过本科研究学分参与该项目的许多方面。

Public AbstractCTS-0522578, PI: Lawrence A. Kennedy, University of Illinois ChicagoPulsed Corona Discharge in Supercritical Carbon Dioxide: Fundamentals and Applications Applications of non-thermal plasmas range from material processing to pollution control. In an effort to increase the density of excited states or reactants, or to process non-gaseous media, the scaling of non-thermal discharges to high pressures, liquids, and multiphase systems is of great interest. Supercritical fluids (SCFs) are a special class of high-density fluids that have been investigated in their own rite due to their unique cleaning and solvating properties. Having densities and transport properties intermediate between the gas and liquid states, SCFs have inherent spatial inhomogeneities and are often referred to as "cluster" fluids. This project investigates the nearly unexplored but practically important area of SCF plasmas and discharges. Plasmas sustained in SCFs are expected to have unique chemical reactivity resulting from both the inherent cluster-fluid properties of SCFs; and radical and ion production through electron impact processes in plasma. Even the most fundamental properties of SCF plasmas are largely uncharacterized; so our ability to leverage their unique properties is severely hindered. The project goal is to investigate and characterize discharge initiation and propagation in SCF plasmas. Experimental investigations on electric discharge initiation in supercritical CO2 are being performed over a wide range of supercritical pressures and temperatures. The streamer breakdown mechanism is being investigated including critical electric field, propagation velocity, diameter, branching, and spark transition. Emphasis is placed on the role of spatial inhomogeneities resulting from the inherent nanoscale clustering on plasma properties. Diagnostics include spatially and temporally resolved ICCD imaging, optical spectroscopy, and Schlieren techniques. A comprehensive database on discharge and streamer parameters in SCFs including breakdown voltages, streamer velocities, and spatial characteristics for SCF plasmas is beginning to be assembled. The broader impact involves advances in science, technology, and education. This study is providing fundamental new insights on streamer propagation in inhomogeneous media incorporating clusters of various size and structure. As such, the work is providing a baseline for others to exploit this new class of SCF plasma, which will compliment research on discharges in high-pressure gases and liquids. The research is also advancing knowledge in related areas of dusty plasmas and microplasmas. From a practical perspective, this research opens the area of non-thermal supercritical plasmas for technological benefit. Exploiting the properties of SCF plasmas will likely extend and improve the technologies that now utilize conventional SCFs. Independently, both non-equilibrium plasmas and SCFs have proven to be exceptional processes for oxidizing, etching parts, pollution removal, material synthesis, sensors, bacteria inactivation and polymerization. The combination of both processes holds the promise of significant synergistic enhancements. Research and education are integrated via mechanisms that will serve several important constituencies, including: graduate and undergraduate students and fellow researchers through opening up a new area of plasma science and engineering. Undergraduate students are involved in many aspects of this project through academic credit for undergraduate research.