Collaborative Research: A Low-Pressure Plasma Process for Nano-Coating of Micron- and Nano-Sized Particles

合作研究：微米级和纳米级颗粒纳米涂层的低压等离子体工艺

• 批准号: 0422900
• 负责人: Farzad Mashayek
• 金额: --
• 依托单位: University of Illinois at Chicago
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2005
• 资助国家: 美国
• 起止时间: 2005-03-01 至 2007-02-28
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0422900&HistoricalAwards=false
• 关键词: Collaborative; Research; Low; Pressure; Plasma

ABSTRACT - 0422900Micrometer and nanometer size particles of various materials are building blocks and important constituents of many chemicals, ceramics and metal composites, pharmaceutical and food products, energy related products such as solid fuels and batteries, and electronics related products. The surfaces of these particles can be altered by coating them with other materials for improving properties such as, adhesion, hydrophobicity, hydrophilicity, printability, corrosion resistance, etc. The goal of this proposal is to design, analyze and optimize a continuous, low-pressure plasma process for the deposition of nanocoatings on nano- and micron-sized particles, by conducting concurrent computational and experimental studies.Low-pressure plasmas are unique in their ability to handle a broad variety of substrate materials, particle sizes and shapes, and gas-phase precursors. They offer the advantage of low temperature processing (300 K to 600 K), wide range of chemistries that can be conducted, excellent purity control compared to liquid-phase processing, and ability to produce surface features in the nanometer range. Further, the non-equilibrium nature of these plasmas produces a population of highly energetic electrons and results in negatively charged dust particles. A consequence of the high degree of charging is the resistance of such particles against aggregation, a problem that usually plagues both liquid and gas-phase processing. Charge stabilization in the plasma is effective for particles as small as 50 nm thus making it possible to process sizes well below the limits of traditional fluidization without the detrimental effects of aggregation.The Co-PI's group has recently demonstrated the feasibility of low-pressure plasma process for depositing films with thickness of the order of a few to several hundred nanometers on micron and sub-micron particles. The existing setup, however, has certain shortcomings: (a) it is characterized by non-uniformities of the deposited film that arise from the immobilization of particles in areas of low reactivity, (b) it is limited in the amount of particulate matter that it can process, and (c) it is not easily amenable to optimization because of the asymmetric electrode design needed to provide stable particle confinement. Here, we propose to use a radially symmetric plasma for continuous film deposition that does not require particles to become trapped in the sheath. In this configuration, the decoupling of gravity from other trapping forces prevents trapping, allowing particles to move continuously through the reactor. The numerical study considers the solution to the Lagrangian equations for plasma (ions and electrons) and dust particles in conjunction with the Eulerian equations for electromagnetic fields, fluid motion, and transport of the precursor and other species in the plasma. The chemical reaction process, leading to particle surface coating, is also modeled and included in the simulations. To adequately address the issue of coating nonuniformity, the plasma particles will be simulated using both the direct method of particle-in-cell (PIC) as well as a more general method involving the solution of the Eulerian equations for ions and electrons in conjunction with a stochastic approach for dust particle charging. The successful design and optimization of the proposed plasma reactor requires the synergy between simulation and experiments. The goal of the numerical part of this work is to establish a realistic model of the dusty plasma, to probe the physics of the process and to explore optimal operation and design for experiments. The goal of the experiments is to establish a continuous production process, to provide input and validation data for the simulation, and to improve the control and quality of the deposited films. The feasibility of the proposed reactor for uniform coating of particles has been demonstrated by conducting a preliminary computational study. The research team covers an interdisciplinary spectrum with extensive modeling and experimental expertise.The broader impacts of the proposed study include potential significant advances in several technological and educational fronts. The development of a continuous production method for the deposition of nanometer-thick layers onto small particles is significant for industrial and

摘要-0422900microter和各种材料的纳米尺寸颗粒是许多化学品，陶瓷和金属复合材料，药品和食品的重要组成部分，固体燃料和电池和电子产品相关的产品。这些颗粒的表面可以通过与其他材料覆盖以改善特性，例如粘附，疏水性，亲水性，可打印性，耐耐药性等。该建议的目的是设计，分析和优化连续的，低压力的等离子体在纳米和纳米构造的纳米构造，并构成纳米大小和微型的纳米构造，以及研究。低压等离子体在处理各种底物材料，粒径和形状以及气相前体的能力方面是独一无二的。它们提供了低温处理（300 K至600 K）的优势，可以进行的化学范围广泛，与液相处理相比，纯度控制良好，以及在纳米范围内产生表面特征的能力。此外，这些等离子体的非平衡性质会产生高能电子的人群，并导致带负电荷的灰尘颗粒。高度充电的结果是这种颗粒对聚集的抗性，这个问题通常困扰着液体和气相处理。 Charge stabilization in the plasma is effective for particles as small as 50 nm thus making it possible to process sizes well below the limits of traditional fluidization without the detrimental effects of aggregation.The Co-PI's group has recently demonstrated the feasibility of low-pressure plasma process for depositing films with thickness of the order of a few to several hundred nanometers on micron and sub-micron particles.然而，现有的设置存在一定的缺点：（a）它的特征是沉积膜的不均匀性，是由于反应性低的区域中固定的颗粒固定而产生的，（b）它可以处理的颗粒物量受到限制，并且（c）不容易优化，因为不需要构成稳定的粒子，因此它可以优化。在这里，我们建议使用径向对称的等离子体进行连续膜沉积，该膜沉积不需要颗粒被困在鞘中。在这种配置中，重力与其他捕获力的解耦可防止捕获，从而使颗粒可以连续通过反应器移动。数值研究考虑了血浆（离子和电子）的拉格朗日方程的解决方案，以及灰尘颗粒以及欧拉尔方程的电磁场，流体运动以及浆液中的前体和其他物种的运输。化学反应过程，导致颗粒表面涂层，也被建模并包括在模拟中。为了充分解决涂层不均匀性问题，将使用直接的粒子中粒子（PIC）方法以及一种更通用的方法来模拟血浆颗粒，该方法涉及离子和电子方程的溶液和电子与尘埃颗粒充电的随机方法结合使用。所提出的血浆反应器的成功设计和优化需要模拟和实验之间的协同作用。这项工作的数值部分的目的是建立一个尘土飞扬的现实模型，以探测过程的物理学并探索实验的最佳操作和设计。实验的目的是建立一个连续的生产过程，为模拟提供输入和验证数据，并提高沉积膜的控制和质量。通过进行初步计算研究，已经证明了所提出的反应器对颗粒均匀涂层的可行性。研究小组涵盖了具有广泛建模和实验专业知识的跨学科谱系。拟议研究的更广泛影响包括在几种技术和教育方面的潜在显着进步。开发一种连续生产方法，用于沉积纳米厚的层到小颗粒上，对于工业和