Compatibility of 3D-Printed Oxide Ceramics with Molten Chloride Salts for High-Temperature Thermal Energy Storage in Next-Generation CSP Plants

Oxide ceramics could be attractive high-temperature construction materials for critical structural parts in high-temperature molten salt thermal energy storage systems due to their excellent corrosion resistance and good mechanical properties. The 3D-printing technology allows the production of ceramic components with highly complex geometries, and therefore extends their applications. In this work, 3D-printed ZrO 2 and Al 2 O 3 ceramics were immersed in molten MgCl 2 /KCl/NaCl under argon or exposed in argon without molten chlorides at 700 °C for 600 h. Their material properties and microstructure were investigated through three-point-bend (3PB) testing and material analysis with SEM-EDX and XRD. The results show that the 3D-printed Al 2 O 3 maintained its mechanical property after exposure in the strongly corrosive molten chloride salt. The 3D-printed ZrO 2 had an enhanced 3PB strength after molten salt exposure, whereas no change was observed after exposure in argon at 700 °C. The material analysis shows that some of the ZrO 2 on the sample surface changed its crystal structure and shape (T→M phase transformation) after molten salt exposure, which could be the reason for the enhanced 3PB strength. The thermodynamic calculation shows that the T→M transformation could be caused by the reaction of the Y 2 O 3 -stabilized ZrO 2 with MgCl 2 (mainly Y 2 O 3 and ZrO 2 with gaseous MgCl 2 ). In conclusion, the 3D-printed ZrO 2 and Al 2 O 3 ceramics have excellent compatibility with corrosive molten chlorides at high temperatures and thus show a sound application potential as construction materials for molten chlorides.