Droplet-Plasma Interactions in Suspension Plasma Spray (SPS) and in Solution Precursor Plasmas Spray (SPPS)

热喷涂工艺是一种使能技术，用于保护组件免受恶劣环境的影响，并显着提高这些组件的性能。由于多种因素的综合作用，例如材料科学的快速进步、增材制造和3D打印的发展，以及气候变化带来的日益严峻的环境挑战。在许多工业领域，与磨损、侵蚀、腐蚀和热效率相关的问题显著增加了制造、维护和运营成本，保护涂层和相关表面技术是战略发展路线图中不可或缺的一部分。例如，2013年，美国国家腐蚀工程师协会估计，仅在美国，腐蚀、磨损和其他材料劣化的成本就超过276亿美元。通过沉积更好的保护涂层，可以大大降低这种巨大的成本。悬浮液和溶液前驱体等离子喷涂（SPS和SPPS）是两种新兴的、非常有前途的涂层技术，可以生产出非常高质量的涂层。在溶液等离子体喷涂（SPS）工艺中，细粉末悬浮在液体中，并被喷涂到高温等离子体射流中。通过将粉末悬浮在液体中，可以避免将细粉末送入热等离子体的正常进料问题。在溶液前驱体等离子体喷雾（SPPS）中，通过将盐溶解在液体中并将其喷射到等离子体射流中来配制前驱体。当液体蒸发时，液滴变得过饱和，导致细颗粒成核，这些细颗粒将被熔化并沉积在衬底上。SPS和SPPS涂料与传统的（粉末）热喷涂涂料相比，显示出相当大的优势。这些工艺沉积的涂层的颗粒尺寸从几十纳米到几微米不等。研究表明，结构精细的涂层具有较好的力学性能、热性能和化学性能。然而，与传统的粉末喷涂工艺相比，SPPS和SPPS要复杂得多，需要进行大量的研究才能更好地了解这两种工艺的细节。特别是，SPS和SPPS液滴如何与等离子体相互作用是理解这些过程的基础。这项为期5年的研究计划提出了两个精确的数学/计算模型，用于在受控条件下单个SPS和SPPS液滴与热等离子体的相互作用。该模型将通过将单个液滴引入新开发的射频电感耦合等离子体火炬（RF-ICP）来验证。利用粒子图像测速技术（PIV），液滴的轨迹将被监测，产生的粒子将被收集在距离火炬出口不同距离的基板上进行分析和表征。

Thermal spray coating process is an enabling technology which is employed to protect components from harsh environments and significantly enhances the performance of these components. Due to a combination of factors, such as rapid progress in materials science, development of additive manufacturing and 3D printing, as well as the increasing environmental challenges being brought on by climate change. Protective coatings and the related surface technologies are an indispensable part of strategic development roadmaps in many industrial sectors in which problems linked to wear, erosion, corrosion and thermal efficiency significantly increase manufacturing, maintenance and operating costs. As an example, in 2013, the US National Association of Corrosion Engineers estimated that the cost of corrosion, wear and other materials deterioration in the US alone exceeded $US 276 B. Such massive costs can be substantially reduced through deposition of better protective coatings. Suspension and solution precursor plasma spraying (SPS and SPPS), which is the subject of the proposed study, are two new emerging and very promising coating technologies that have produced very high-quality coatings. In the solution plasma spray (SPS) process, fine powders are suspended in a liquid and are sprayed into a high temperature plasma jet. By suspending the powder in a liquid, normal feeding problems associated with feeding fine powders into a thermal plasma are avoided. In the solution precursor plasma spray (SPPS), a precursor is formulated by dissolving salts in a liquid and spraying them into a plasma jet. As the liquid evaporates, the droplets become supersaturated, resulting in the nucleation of fine particles that will be melted and deposited onto a substrate. SPS and SPPS coatings have shown considerable advantages over the traditional (powder) thermal spray coatings. These processes deposit coatings with a particle size ranging from a few tens of nanometers to just a few micrometers. It has been shown that finely structured coatings have better mechanical, thermal and chemical properties. However, compared to the traditional powder spray coating process, SPPS and SPPS are far more complicated and much research is needed to better understand the details of these two processes. In particular, how do SPS and SPPS droplets interact with plasma is fundamental to understanding of these processes. This 5-year research program proposes the development of two accurate mathematical/computational models of the interaction of a single SPS and SPPS droplet with a thermal plasma under controlled conditions. The models will be validated by introduction of single droplets into a newly developed radio frequency inductively coupled plasma torch (RF-ICP). Employing particle image velocimetry (PIV), the droplet's trajectory will be monitored, the generated particles will be collected on a substrate at different distances from the torch exit for analysis and characterization.