Characterization of corrosion resistance of C/C–SiC composite in molten chloride mixture MgCl2/NaCl/KCl at 700?°C

摘要

Due to their high thermal stability and low cost, molten chlorides are promising high-temperature fluids for example for thermalenergy storage (TES) and heat transfer fluid (HTF) materials in concentrated solar power (CSP) plants and other applications.However, the commercial application of molten chlorides is strongly limited due to their strong corrosivity against commercialalloys at high temperatures. The work addresses on a fundamental level whether carbon based composite ceramics could bepotentially utilized for some corrosion critical components. Liquid silicon infiltration (LSI) based carbon fiber reinforced siliconcarbide (called C/C–SiC) composite is immersed in a molten chloride salt (MgCl2/NaCl/KCl 60/20/20 mole%) at 700 °C for 500 hunder argon atmosphere. The material properties and microstructure of the C/C–SiC composite with and without exposure in themolten chloride salt have been investigated through mechanical testing and analysis with scanning electron microscopy (SEM) andenergy-dispersive X-ray (EDX) scanning. The results reveal that the C/C–SiC composite maintains its mechanical properties afterexposure in the strongly corrosive molten chloride salt. The oxidizing impurities in the molten salt react only with residualelemental silicon (Si) in the area of the C/C–SiC matrix. In comparison, no indication of reaction between the molten chloride saltand carbon fiber or SiC in the matrix is observed. In conclusion, the investigated C/C–SiC composite has a sound applicationpotential as a structural material for high-temperature TES and HTF with molten chlorides due to its excellent corrosion resistanceand favorable mechanical properties at high temperatures.