Plasma and HVOF Spray of Colloidal Solutions to Create Nano-Scale Features in Coatings

本研究的目的是开发一种新的注射技术，将允许快速和廉价的制造涂层组成的纳米级功能。几乎任何可以分散在溶剂中并熔化的材料都可以使用该工艺制造。该方法是将纳米级粉末分散在溶剂中以形成胶体浆料，然后将浆料喷射到等离子体或高速氧燃料（HVOF）产生的羽流中以蒸发溶剂并熔化粉末。粉末在火焰中的向前运动使它们撞击基底并变平，形成纳米级的“薄片”，并迅速固化。将研究控制薄片形态和晶粒尺寸的工艺变量，包括浆料特性（粉末尺寸和溶剂中的粉末装载量）、注射喷嘴类型、羽流类型以及衬底温度和类型。将使用X射线衍射、透射电子显微镜、原子力显微镜和扫描电子显微镜研究所得的微观结构。这些纳米级液滴的冲击和固化行为的建模将被执行，以补充实验工作。热障涂层（TBCs）保护燃气涡轮机发动机中的金属结构不受极端温度的影响，在美国经济的运输（商用飞机）和能源（发电）部门中发挥着重要作用。使用热障涂层可以使燃气轮机在更高、更省油的温度下运行。通过使用新的注射技术来制备具有纳米晶特征的热障涂层，将证明当晶粒尺寸接近声子波长时，热导率可以显着降低。这将进一步提高热障涂层保护燃气轮机金属结构的有效性。结合在大学建立的一个特殊的本科生研究计划，这一建议将为本科生提供从事研究的机会。

The objective of this research is to develop a novel injection technology that will allow quick and inexpensive fabrication of coatings comprised of nanoscale features. Virtually any material that can be dispersed in a solvent and that melts can be manufactured using this process. The approach is to disperse nanosized powders in a solvent to form a colloidal slurry, then spray the slurry into a plasma or a high velocity oxygen fuel (HVOF) generated plume to evaporate the solvent and melt the powder. The forward motion of the powders in the flame causes them to strike the substrate and flatten, forming nanosized "lamellae," which quickly solidify. The processing variables that control lamellae morphology and grain size, include slurry characteristics (powder size and powder loading in the solvent), injection nozzle style, plume type, and substrate temperature and type will be investigated. The resulting microstructure will be studied using X-ray diffraction, transmission electron microscopy, atomic force microscopy, and scanning electron microscopy. Modeling of the impact and solidification behavior of these nanoscale droplets will be performed to compliment the experimental work.Thermal barrier coatings (TBCs), which protect the metallic structure in a gas turbine engine from temperature extremes, play an important role in the transportation (commercial aircraft) and energy (electricity generation) sectors of the U.S. economy. The use of TBCs allows gas turbines to be operated at higher, more fuel-efficient temperatures. By using the novel injection technology to prepare TBCs with nanocrystalline features it will be demonstrated that thermal conductivity can be significantly reduced as grain sizes approach phonon wavelengths. This will further increase the effectiveness of TBCs to protect the metallic structure of gas turbines. In conjunction with a special undergraduate research program established at the university, this proposal will provide engaging research opportunities for undergraduates.