Preparation of Ultra-Low Thermal Conductivity Coatings Via Suspension Plasma Spray Using a Defect Clustering Approach

这项研究的目的是研究一种新的加工方法来生产超低导电性热障涂层，以克服目前氧化钇稳定氧化锆涂层的不足。热障涂层用于燃气涡轮发动机，以热保护燃烧区域的高温合金叶片，提供更热，更有效的工作温度。我们制备下一代热障涂层的方法首次结合了两种新开发的技术：悬浮等离子喷涂和缺陷聚类。在悬浮等离子体喷雾中，纳米级粉末分散在乙醇中形成胶体悬浮液；然后将悬浮液喷射到热等离子体羽流中以蒸发溶剂并熔化粉末。第二种技术，缺陷聚类，涉及到在等离子喷涂涂层中掺杂钇稳定的氧化锆和成对的稀土离子（如钇和钕），以形成不移动的簇。热障涂层中这些团簇的存在使声子散射，与目前的氧化钇稳定的纯氧化锆涂层相比，涂层的导热系数降低了一半以上。如果成功，这项研究的结果将允许燃气涡轮发动机在更高、更省油的温度下运行，节省燃料并减少能源使用。从这项研究中出现的新涂层设计有可能影响那些关注寻找最便宜的方法来运输人员和货物以及生产能源的关键行业。在教育影响方面，这项资助的主要研究者通过先前的NSF支持，在研究生、本科生和高中阶段大量参与指导。这笔拨款将通过提供研究机会，为所有三组学生继续这些努力。

The objective of this research award is to investigate a novel processing method to produce ultra-low conductivity thermal barrier coatings that would overcome the deficiencies of current yttria-stabilized zirconia coatings. Thermal barrier coatings are used in gas turbine engines to thermally protect the superalloy blades in the combustion area, affording hotter, more efficient operating temperatures. Our approach for preparing next generation thermal barrier coatings couples for the first time two newly developed techniques: suspension plasma spray and defect clustering. In suspension plasma spray, nanosized powders are dispersed in ethanol to form a colloidal suspension; the suspension is then sprayed into a hot plasma plume to evaporate the solvent and melt the powder. The second technique, defect clustering, involves doping yttria-stabilized zirconia with paired rare-earth ions (such as ytterbium and neodymium) to create immobile clusters in the plasma-sprayed coating. The presence of these clusters in a thermal barrier coating scatters phonons, reducing coating thermal conductivity by over one-half compared to current yttria-stabilized zirconia-only coatings. If successful, the results of this research will allow gas turbine engines to be operated at higher, more fuel efficient temperatures, saving fuel and reducing energy usage. New coating designs emerging from this research have the potential to influence key industries that are concerned with finding the least expensive method to transport people and goods and produce energy. In terms of educational impact, the primary investigator for this grant is heavily involved in mentoring at the graduate, undergraduate, and high school levels through prior NSF support. This grant would continue these efforts for all three groups of students by providing research opportunities.