Abstract
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.
Highlights
Molten chlorides are promising next-generation high-temperaturethermal energy storage (TES) and heat transfer fluid (HTF) materials in, for example, nextgeneration concentrated solar power (CSP) plants [1]
It was reported that even the Ni-based superalloys like Hastelloy cannot meet the requirements of corrosion resistance in commercial applications when they contact with molten chlorides at high temperatures under inert atmosphere (e.g., MgCl2 /NaCl/KCl at 700 ◦ C) [3,4,5,6,7]
The effect of the molten salt exposure on the 3D-printed ZrO2 and Al2 O3 ceramics is discussed based on the tests and analysis, in order to determine if they can be used as construction materials in contact with strongly corrosive molten chloride salts
Summary
Thermal energy storage (TES) and heat transfer fluid (HTF) materials in, for example, nextgeneration concentrated solar power (CSP) plants [1]. The oxide ceramics are often used for molten chloride laboratory experiments (e.g., corrosion, electrochemistry, crucibles) [10,13] They could be attractive high-temperature construction materials for critical structural parts in contact with strongly corrosive molten salts (e.g., moving parts such as pump bearings [14], seals, electrical insulators and hot surfaces). Compared to ceramic composites, the 3D-printed oxide ceramics like ZrO2 can have much lower porosity (
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