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

• Published in: Energies (Basel) 2021-05, Vol.14 (9), p.2599
• Main Authors: Ding, Wenjin, Shi, Yuan, Braun, Markus, Kessel, Fiona, Frieß, Martin, Bonk, Alexander, Bauer, Thomas
• Format: Article
• Language: English
• Subjects: 3-D printers; 3D-printed ZrO2 and Al2O3 ceramics; Aluminum oxide; Bend properties; Ceramics; Chloride; Compatibility; concentrated solar power (CSP); Construction materials; Corrosion resistance; Corrosion tests; Crystal structure; Energy storage; Exposure; Genetic transformation; Heat exchangers; Heat resistance; High temperature; Magnesium chloride; Manufacturing; Material properties; Mechanical properties; Microscopy; molten salt; Molten salts; Potassium chloride; Salts; Sodium chloride; Storage systems; Thermal energy; three-point-bend strength (3PB strength); Yttria-stabilized zirconia; Yttrium oxide; Zirconium dioxide
• ISSN: 1996-1073; 1996-1073
• DOI: 10.3390/en14092599

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.