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的结构表面和块体部件中变得越来越重要。例如，使用纳米晶金属不锈钢粉末的喷涂涂层与常规涂层相比表现出上级硬度，并且纳米结构的Al基块体合金表现出约两倍于商业对应物的拉伸强度。各种方法，如激光沉积，热喷涂和等离子喷涂，已在实验室中开发，以获得纳米结构涂层。然而，迄今为止，还没有用于工业应用的纳米级粉末涂料技术可商业化。正在进行的研究集中在一个新的和创新的静电力辅助冷气体动态喷涂（ECGDS）技术，用于生产纳米结构涂层在低温下，低成本和高产量。这项工作的智力价值包括将传统的CGDS系统的微米级颗粒扩展到纳米级颗粒尺寸谱。它将静电场与超声速气固两相动态流场相结合，为纳米粒子提供足够的动量，使其穿透弓形激波，然后以足够的动能在靶面上存款。研究工作的目标是调查ECGDS的可行性，了解纳米粒子在超音速流中的传输过程，并通过密集的数值模拟和实验研究将喷雾参数（包括纳米粒子尺寸、载气、气体压力和气体温度）与所得涂层的密度和结构相关联。该提案的创新包括使用静电力来帮助纳米颗粒加速穿透弓形冲击，防止纳米颗粒团聚的技术，以及将纳米颗粒充电到高水平的新充电器。这个SGER-GOALI项目预计将对UWM以及大密尔沃基地区的研究和教育产生重大而广泛的影响。ECGDS系统是开发新的低温涂层技术的重要工具，这将直接影响许多工业应用，如燃料电池。纳米粒子的生产，分散和充电的结果将显着有助于基于纳米粒子的纳米制造和纳米织物的一般领域。该GOALI项目将与国际热力系统公司（ITS，GOALI合作伙伴）共同开发，如果成功，该技术将直接转移到工业领域。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UWM的进一步教育工作。这项工作也影响了UWM的课程。

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.