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7366 |
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Friday, May 06, 2022, Hall D 2:20 PM Suspension Spraying II |
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Current trends in the development of suspensions and liquid precursors for thermal spraying |
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Annegret Potthoff / Fraunhofer Institute for Ceramic Technologies and Systems (IKTS), Germany Anja Meyer* / Fraunhofer IKTS, Germany Filofteia-Laura Toma/ Fraunhofer IWS, Germany Oliver Kunze/ Technische Universität Dresden, Germany |
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When compared with conventional thermal spraying processes, thermal spraying of suspensions allows producing coatings with outstanding properties in terms of microstructure, surface topography, and phase compositions, as well as mechanical, electrical or tribological properties. The use of suspensions as feedstock results in an almost unlimited flexibility in the chemical composition of the sprayed coatings. Moreover, thermal spraying of suspensions is a promising technique for processing of expensive raw materials. The substitution of rarely available powders by common raw materials followed by an in-situ chemical reaction while spraying leads to the formation of the wished coating composition. Zn2TiO4 coatings are an example, where the expensive costs of blended oxide powders as feedstock material hinders the market introduction, whereas outstanding electrical properties and photocatalytic activity of thermally sprayed Zn2TiO4 coatings are of interest for various industrial applications. Thermal spraying of tailor-made binary suspensions from (i) a mixture of two suspensions containing ZnO and TiO2 (anatase or rutile) particles, respectively or (ii) a substitution of one of the components by a precursor solution is an appropriate way to form Zn2TiO4 coatings with both, excellent properties, and reasonable prices. Promising mixtures of raw materials are identified by analyzing chemical reactions during spraying process. To follow the formation of the compositions in the system ZnO-TiO2 differential thermal analysis (DTA) and thermal gravimetry (TG) measurements are performed. Preparation routes of stable suspensions with low sedimentation rates and good flow behavior are presented. The composition of resulting coatings is determined by XRD and XRF analysis. It was showed, that Zn2TiO4 has been formed during S-HVOF spraying. This work shows the potential to develop appropriate cost-effective suspension feedstock from single oxide raw materials or precursor salts to obtain Zn2TiO4-coatings. |