Investigation of the deposition mechanism for the aerosol deposition of ceramics by evaluating of the processes that occur when micrometer-sized particles impact on surfaces

近年来，出现了一种制备致密陶瓷涂层的新工艺，与传统的高温工艺相比具有一些优点。为了制造陶瓷部件和涂层，通常需要1000°C以上的烧结温度。因此，陶瓷层很难应用于低熔点的金属、玻璃或聚合物。采用这种新工艺，即所谓的气溶胶沉积法(ADM)，可以从相应的粉末直接沉积陶瓷层。这是一个完全冷的过程，既不需要加热载气，也不需要加热粉末或衬底。为此，粉末被雾化并沉积到表面，然后在朝向它的喷流中被涂覆。然而，形成层的确切机制尚不清楚。到目前为止，人们已经知道，颗粒的高动能，理想情况下直径在几百纳米到几微米之间，当与底物碰撞时，会导致碎裂成纳米大小的碎片。在衬底上形成的锚固层导致该层的连续堆积和致密化。这一过程被称为室温冲击固结(RTIC)。在通过冲击破碎来研究颗粒团聚体的强度时，可以观察到类似的现象。它们在所谓的冲击器中高速分离，从喷流到表面。在这里，颗粒对载体表面的影响显然导致了到目前为止还没有被充分理解的过程。特别是，撞击过程中粒子反弹的现象还没有完全被理解。颗粒和撞击板的屈服压力在这里起作用。此外，由于接触荷电现象，颗粒会产生静电荷电，这也会通过库仑与冲击板的相互作用影响沉积效率。然而，基于宏观材料性质的预测通常不能解释实验观察。两个PI进行了大量前期工作的两个过程的比较显示，无论是实验结果还是问题都有很大的重叠。因此，拟议的实验项目的总体目标是更好地了解粒子撞击到它们并入固体薄膜之间发生的过程。这将更好地解释气溶胶颗粒撞击破碎的结果，通过撞击更精确地控制颗粒层的形成，提高ADM陶瓷层的质量。

In recent years, a new process has emerged to produce dense ceramic coatings, which has some advantages over the well-established high-temperature processes. In order to manufacture ceramic components and coatings, sintering temperatures of over 1000 °C are usually required. As a result, ceramic layers can hardly be applied to low-melting metals, glasses or polymers. With the new process, the so-called Aerosol Deposition Method (ADM), the ceramic layers can be deposited directly from the corresponding powder. It is a completely cold process, in which neither carrier gases nor powders or substrates need to be heated. For this purpose, the powder is aerosolized and deposited onto the surface to be coated in a jet flow directed towards it.However, the exact mechanism of layer formation remains unclear. So far, it has been known that the high kinetic energy of the particles, which ideally have diameters in the range from a few hundred nm to a few micrometers, leads to fragmentation into nanometer-sized fragments upon impact with the substrate. The formation of an anchoring layer on the substrate leads to a continuous build-up and densification of the layer. This process is known as Room Temperature Impact Consolidation (RTIC).Similar phenomena can be observed during the investigation of the strength of particle agglomerates by impact fragmentation. They are separated at high speeds in a so-called impactor from a jet flow onto a surface. Here, too, the impact of the particles on the carrier surface obviously leads to processes that have so far been inadequately understood. In particular, the phenomenon of particle bounce during impaction has not yet been fully understood. The yield pressure of the particles and the impaction plate play a role here. In addition, electrostatic charging of particles can occur due to the phenomenon of contact charging, which can also influence the deposition efficiency via Coulomb interactions with the impaction plate However, predictions based on macroscopic material properties often do not explain the experimental observations.A comparison of the two processes, in which the two PIs conducted much preliminary work, reveals a large overlap both with regard to the experimental findings and to the problems. The overall aim of the proposed experimental project is therefore to understand the processes better that occur between the impact of the particles and their incorporation into a solid film. The results of the impact fragmentation of aerosol particles will be better interpreted and the formation of particle layers will be more precisely controlled by impaction and the quality of ceramic layers from the ADM will be improved.