New Opportunities for the Aerosol Deposition Method by Substrate by Cryogenics

• Applicant: Professor Dr.-Ing. Ralf Moos
• Subject Area: Coating and Surface Technology ; Synthesis and Properties of Functional Materials
• Term: from 2017 to 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 388538917

Dense ceramic coatings in the range from 1 to 300 µm can be applied directly from ceramic powders without high temperature processes on almost any substrate materials using the aerosol deposition method (ADM), which is known in German as "aerosolbasierte Kaltabscheidung (room temperature impact consolidation)". Even ceramic coatings with low melting metals, glasses or very hard polymers can coated. The material properties of the deposited layer are thereby similar to the source material.In the ADM community it is repeatedly observed that the hardness difference between substrate and coating material as well as the mechanical properties of the substrate are key influencing factors for the ADM deposition success. Own observations suggest that softer materials can be deposited more easily and with much larger thicknesses on ceramics as harder ceramics. It seems that a certain minimum substrate hardness and substrate toughness must exist to deposit the powder as a dense adhesive film.In this project, we want to vary the mechanical properties of the substrate and the coating material by temperature variation, especially by cooling of the substrate or the powder over a large temperature range down to 77 K to investigate the effect of the mechanical properties on the ability to form high quality films. So far, only works are known, which explain the (negative) impact of an increase in substrate temperature.The project is planned for a period of two months (with required funding for only 18 person month). It starts with the modification of one of the chair's ADM coating machines so that powder and substrate cooling is possible. In order to determine the effect of temperature on the coating behavior, the actual coating tests are then carried out in the form of a test matrix at different temperatures for five substrate materials and four powders in a way that by temperature variations of substrate and powder material the deposition window is adjusted. For that purpose, materials that exhibit a large change in the mechanical properties in the low-temperature range are used.At the end of the project, a conceptual proof should have been provided showing that the cryogenics ADM improves the layer formation (higher deposition rates or higher layer quality) or allows an extension of the process window (deposition of materials that can otherwise not be deposited by ADM).

• DFG Programme: Research Grants