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 - 0422900各种材料的微米和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、能源相关产品（例如固体燃料和电池）以及电子相关产品的构建块和重要成分。这些颗粒的表面可以通过用其他材料涂覆来改变，以改善其性能，如粘附性、疏水性、亲水性、可印刷性、耐腐蚀性等。该提案的目标是通过同时进行计算和实验，设计、分析和优化连续的低压等离子体工艺，用于在纳米和微米尺寸的颗粒上沉积纳米涂层。 低压等离子体具有独特的能力，可以处理各种基材材料、颗粒尺寸和形状以及气相前驱体。它们具有低温处理（300 K 至 600 K）、可进行多种化学反应、与液相处理相比具有出色的纯度控制以及产生纳米范围表面特征的能力等优点。此外，这些等离子体的非平衡性质会产生大量高能电子，并产生带负电的尘埃颗粒。高充电程度的结果是此类颗粒对聚集的抵抗力，这是一个通常困扰液相和气相加工的问题。等离子体中的电荷稳定对于小至 50 nm 的颗粒是有效的，因此可以处理远低于传统流化极限的尺寸，而不会产生不利的聚集影响。Co-PI 的小组最近证明了低压等离子体工艺在微米和亚微米颗粒上沉积厚度为几到几百纳米的薄膜的可行性。然而，现有装置具有某些缺点：(a) 其特点是沉积膜不均匀，这是由于颗粒固定在低反应性区域而产生的；(b) 其可处理的颗粒物数量有限；(c) 由于需要提供稳定的颗粒限制所需的不对称电极设计，因此不易进行优化。在这里，我们建议使用径向对称等离子体进行连续薄膜沉积，不需要将颗粒捕获在鞘中。在这种配置中，重力与其他捕获力的解耦可以防止捕获，从而允许颗粒连续移动通过反应器。数值研究考虑了等离子体（离子和电子）和尘埃粒子的拉格朗日方程的解，以及电磁场、流体运动以及等离子体中前体和其他物质的传输的欧拉方程。导致颗粒表面涂层的化学反应过程也被建模并包含在模拟中。为了充分解决涂层不均匀性问题，将使用颗粒在细胞 (PIC) 的直接方法以及涉及求解离子和电子的欧拉方程以及灰尘颗粒充电的随机方法的更通用方法来模拟等离子体颗粒。所提出的等离子体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标是建立尘埃等离子体的真实模型，探索该过程的物理原理并探索实验的最佳操作和设计。实验的目标是建立连续的生产过程，为模拟提供输入和验证数据，并提高沉积薄膜的控制和质量。通过进行初步的计算研究，已经证明了所提出的颗粒均匀涂覆反应器的可行性。该研究团队涵盖跨学科领域，具有广泛的建模和实验专业知识。拟议研究的更广泛影响包括多个技术和教育领域的潜在重大进展。开发将纳米厚层沉积到小颗粒上的连续生产方法对于工业和应用具有重要意义。