Optical in situ diagnostics of droplets, nanoparticles and aggregates in spray-flame synthesis

喷雾火焰合成纳米颗粒的产物性能不仅取决于其化学成分，而且在很大程度上取决于其颗粒形态。在该项目中，采用先进的激光光学方法来研究颗粒的生长和聚集，并将颗粒性质与合成的边界条件（前驱体类型、浓度、溶剂、体积流量）联系起来。因此，它可以对过程理解做出重大贡献。在项目的第一阶段，对广角光散射（WALS）方法进行了改进，以测量喷雾火焰中的液滴尺寸。在这个项目阶段，评估例程将进一步改进，以便更准确和更快地确定。WALS方法也用于原位测量纳米颗粒和聚集体在火焰扩展范围内的特性（旋转半径、分形维数）。对于选定的材料系统（特别是氧化铁），这些研究是通过使用时间分辨激光诱导白炽灯（TiRe-LII）来测量主要粒度的补充，从而确定工艺链所需的关键特性。组合测量技术还用于研究各种问题，这些问题已经成为关注的焦点，特别是由于SPP小组的工作。一方面，这些问题涉及根据溶剂的组成形成颗粒的首选路径（直接从液滴或从气相）。另一方面，研究了在此过程中观测到的脉动对粒子性能的影响。为此，将时间分辨火焰发光与在单镜头模式下进行的WALS测量相结合并进行相关。除了与中央项目就材料系统、工艺条件和数据进行交流外，还与SPP的几个实验工作组进行合作，直接提供相互补充的数据。此外，与在数值模拟领域工作的小组的合作已经达成一致，并确定了第一个相互感兴趣和可访问的材料系统。一方面，该项目的数据用于直接验证模拟，另一方面，数值项目提供了进一步的信息，例如粒度分布的形式，以便基于模型从而改进对WALS数据的评估。

The product properties of nanoparticles from spray flame synthesis (SFS) do not only depend on their chemical composition but also to a large extent on their particle morphology. Within the project advanced laser optical methods are employed to investigate particle growth and aggregation and correlates particle properties with the boundary conditions of the synthesis (precursor type, concentration, solvent, volume flow). It can thus make a significant contribution to process understanding. In the first phase of the project, the method of Wide-Angle Light Scattering (WALS) approach was enhanced to measure droplet sizes in the spray flame. In this project phase, evaluation routines will be further improved allowing for a more accurate and faster determination. The WALS method is also used for in situ measurement of the characteristics of nanoparticles and aggregates (radius of gyration, fractal dimension) in an extended range of the flame. For selected material systems (especially iron oxide) these investigations are complemented by the use of time-resolved Laser-Induced Incandescence (TiRe-LII) for the measurement of primary particle size, allowing for the determination of key properties essential for the process chain. The combined measurement techniques are also used to investigate various questions which have come into the focus of interest especially due to the work of the groups in the SPP. On the one hand, these concern the formation of a preferred route of particle formation (directly from droplets or from the gas phase) depending on the composition of the solvent. On the other hand, the effect of pulsations observed in the process on the particle properties is investigated. For this purpose, time-resolved flame luminescence is combined and correlated with WALS measurements, which are performed in single shot mode.In addition to the exchange with the central project regarding material systems, process conditions and data, a cooperation with several experimentally working groups of the SPP is carried out to directly provide mutually complementary data. Furthermore, collaboration with groups working in the field of numerical simulation have been agreed upon and first mutually interesting and accessible material systems have been defined. On the one hand, the data of this project serve for the direct validation of the simulation, on the other hand the numerical projects provide further information, e.g. on the form of a particle size distribution, to enable a model-based and thus improved evaluation of the WALS data.