Hetero-aggregation of fine particles in supersonic flow for the tailor-made surface coating

计划中的实验和理论研究的目标是开发和描述不同亚微米颗粒在超音速流动中混合和脱湿的异相聚集过程，以获得定制的表面涂层。为此，在气相中通过非均相去升华过程产生异相聚集体。在气体通过拉瓦尔喷嘴膨胀为超音速流动之前，一种材料在气相中被强大的加热器升华。由于压力和温度的强烈降低，气相过饱和，核心颗粒发生脱升，进入膨胀室的回流区，并输送到过饱和度最高的区域。组分的混合行为决定了异质聚集颗粒的形状和大小。利用扫描迁移率粒子谱仪(SMPS)和扫描电子显微镜(SEM)对生成的异相聚集体进行了表征。3D光散射传感器将用于在线测量颗粒形状。通过计算流体动力学(CFD)和离散元方法(DEM)的跨尺度模拟，研究了复杂的流动行为和集合体结构。采用纳米压痕技术研究了异质骨料的力学变形和破坏行为，并用离散元方法对其进行了模拟。生成的异质聚集体将用于通过热喷涂沉积过程在墙壁表面形成异质涂层。涂层的力学性能将通过纳米压痕进行研究。

The goal of the planned experimental and theoretical research is the development and description of a hetero-aggregation process of different submicron particles by mixing and desublimation in a supersonic flow for a tailor-made surface coating. For this purpose, hetero-aggregates are generated in the gas phase by a heterogeneous desublimation process. One material is sublimated in the gas phase by a powerful heater before the gas is expanded through a Laval nozzle to a supersonic flow. Due to the strong pressure and temperature reduction, the gas phase is supersaturated and the desublimation on core particles takes place, which are given into a backflow region of the expansion chamber and transported to the region of the highest supersaturation. The mixing behaviour of the components determines the shape and size of the hetero-aggregated particles. The generated hetero-aggregates are characterized according to their size distribution by Scanning Mobility Particle Spectrometer (SMPS) and Scanning Electron Microscopy (SEM). The 3D Light Scattering Sensor will be used for the inline measurement of the particle shape. The complex flow behaviour and aggregate structure are investigated by cross-scale simulations of Computational Fluid Dynamics (CFD) and the Discrete Element Method (DEM). The mechanical deformation and breakage behaviour of hetero-aggregates is studied by nanoindentation and simulated by DEM. The generated hetero-aggregates will be used for the creation of hetero-coatings on wall surfaces by a thermal spraying deposition process. The mechanical properties of the coating layer will be studied by the nanoindentation.