Aerosol Deposition Method: Co-deposition of functional materials and fillers to replace a subsequent thermal treatment

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This project includes further fundamental investigations on the process of aerosol deposition of ceramic powders, also known as aerosol deposition method (ADM), that are based on more recent findings of the deposition mechanism. For example, reduced functional properties compared to bulk material (especially with regard to ionic or electronic conductivity) can be observed for all coatings produced by ADM directly after deposition. By means of a thermal post-treatment after the AD process, these properties can be permanently restored so that the properties of the films reach permanently the properties of the bulk material. The temperatures required for this improvement are significantly below the temperature required for grain growth. The reason for the poorer functional properties of AD coatings directly after coating is the process-related generation of mechanical micro-stresses during layer formation. This is the point at which the present application comes into play. The focus here is on reducing or completely avoiding thermal treatment that follows the AD process. This is to be made possible by adding chemically and electrically inert fillers (CaF2, PE/PP and Al2O3) to the functional materials (YSZ, STF). The filler material has the function of a mechanical buffer material, whereby a reduction of the layer-immanent micro-stresses is achieved. The exact influence of the filler material on the coating process is currently unclear. In order to qualitatively and quantitatively assess the correlation between the inert filler and the functional material on the properties of the layer, several filling materials and two functional materials are combined with each other. ADM is carried out as a co-deposition of powder mixtures. In addition, the mixing ratios of the corresponding powder mixtures are varied. With increasing addition of filler material, it is assumed that on the one hand film-immanent tensions can be reduced. On the other hand, however, dilution occurs and the functional properties of the coating, which are based on the functional material, are reduced. In order to achieve the highest possible proportion of functional material in the mixture, the construction of a gradient layer is an integral part of the last part of the project. Depending on the thickness of the coating, the proportion of functional material in the mixture is to be varied in order to create thick layers with minimal stresses and a high proportion of functional material.The investigations in the course of the project are intended to broaden the fundamental understanding of the layer formation process, whereby in future new, especially low melting point components combined with good functional properties can be bonded by means of aerosol deposition at room temperature.