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

• Main Authors: Wenjin Ding, Yuan Shi, Markus Braun, Fiona Kessel, Martin Frieß, Alexander Bonk, Thomas Bauer
• Format: Article
• Language: English
• Published: MDPI AG 2021-05-01
• Series: Energies
• Subjects: concentrated solar power (CSP); 3D-printed ZrO₂ and Al₂O₃ ceramics; three-point-bend strength (3PB strength); corrosion resistance; molten salt
• Online Access: https://www.mdpi.com/1996-1073/14/9/2599

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 ZrO₂ and Al₂O₃ ceramics were immersed in molten MgCl₂/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 Al₂O₃ maintained its mechanical property after exposure in the strongly corrosive molten chloride salt. The 3D-printed ZrO₂ 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 ZrO₂ 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 Y₂O₃-stabilized ZrO₂ with MgCl₂ (mainly Y₂O₃ and ZrO₂ with gaseous MgCl₂). In conclusion, the 3D-printed ZrO₂ and Al₂O₃ ceramics have excellent compatibility with corrosive molten chlorides at high temperatures and thus show a sound application potential as construction materials for molten chlorides.