SGER/GOALI: Electrostatic-Force-Assisted Cold Gas Dynamic Spray of Nanoparticles-A New Low Temperature Process for Producing Nanostructured Coatings and Bulk Materials

纳米结构涂层和块体材料在开发新型结构表面和块体部件方面变得越来越重要。例如，与传统涂层相比，使用纳米晶金属不锈钢粉末的喷涂涂层具有更高的硬度，纳米结构al基大块合金的抗拉强度约为商业同类产品的两倍。各种方法，如激光沉积、热喷涂和等离子喷涂，已经在实验室中开发出来，以获得纳米结构涂层。然而，到目前为止，还没有工业应用的纳米级粉末涂层技术商业化。研究的重点是一种新的创新的静力辅助冷气体动态喷涂（ECGDS）技术，用于在低温下生产低成本、高通量的纳米结构涂层。这项工作的智力价值在于将传统的微颗粒CGDS系统扩展到纳米级粒度谱。它将静电场与超声速气粒两相动力流场相结合，为纳米颗粒穿透弓形激波提供了足够的动量，并以足够的动能沉积在目标表面。本研究的目的是研究ECGDS的可行性，了解纳米颗粒在超声速流动中的输运过程，并通过大量的数值模拟和实验研究，将纳米颗粒尺寸、载气、气体压力和气体温度等喷雾参数与所得涂层的密度和结构联系起来。该提案的创新包括使用静电力来帮助纳米粒子加速穿透弓形冲击，防止纳米粒子聚集的技术，以及一种新的充电器来给纳米粒子充电到高水平。这个SGER-GOALI项目预计将对威斯康星大学和大密尔沃基地区的研究和教育产生重大而广泛的影响。ECGDS系统是开发新型低温涂层技术的重要工具，它将直接影响燃料电池等许多工业应用。纳米粒子的产生、分散和充电的研究结果将对基于纳米粒子的纳米制造和纳米加工的一般领域做出重大贡献。该GOALI项目将与国际热系统公司（ITS， GOALI合作伙伴）共同开发，如果这项技术成功，将直接转移到工业上。该项目通过本科生、研究生和K-12教师，特别是代表性不足的少数民族的参与，促进了威斯康星大学进一步的教育工作。这项工作也影响了威斯康星大学的课程设置。

Nanostructured coatings and bulk materials have become increasingly important in developing new structural surfaces and bulk components. For instance, sprayed coatings using nanocrystalline metallic stainless steel powders exhibit superior hardness compared to conventional coatings, and nanostructured Al-based bulk alloy exhibits tensile strength about twice that of the commercial counterparts. Various methods, such as laser deposition, thermal spray, and plasma spray, have been developed in the laboratory to obtain nanostructured coatings. However, to date no nanoscale powder coating technologies for industrial applications are commercially available yet. The research being conducted is focused on a new and innovative electrostatic-force-assisted cold gas dynamic spray (ECGDS) technique for producing nanostructured coatings at low temperature with low cost and high throughput. The intellectual merit of the work involves the extension of the conventional CGDS system for micro-sized particles to the nanoscale particle size spectrum. It combines the electrostatic field with the supersonic gas-particle two-phase dynamic flow field to provide sufficient momentum for nanoparticles to penetrate through the bow shock and then deposit on the target surface with sufficient kinetic energy. The objectives of the research effort are to investigate the feasibility of the ECGDS, to understand the transport process of nanoparticles in the supersonic flow, and to correlate the spray parameters, including nanoparticle size, carrier gas, gas pressure, and gas temperature, with the density and the structure of the resulted coating through intensive numerical simulations and experimental studies. Innovations of the proposal include use of electrostatic force to assist nanoparticle acceleration to penetrate the bow shocks, techniques to prevent agglomeration of nanoparticles, and a new charger to charge nanoparticles to high levels. This SGER-GOALI project is expected to have a significant and broad impact on research and education at UWM as well as in the Great Milwaukee Area. The ECGDS system is an essential tool for the development of new low temperature coating technology, which will directly impact many industrial applications, such as fuel cells. Results on the nanoparticle production, dispersion, and charging will significantly contribute to the general area of nanoparticle-based nanomanufacturing and nanofabrication. This GOALI project will be co-developed with International Thermal Systems (ITS, GOALI partner), and this technology, if successful, will be transferred directly to industry. The project promotes further educational efforts at UWM through the participation of undergraduates, graduates and K-12 teachers, particularly underrepresented minorities. The work is also impacting the curriculum at UWM.