Microscale probing of molten salts crystallization: A pathway to efficient thermal energy storage

Molten salts are important heat storage media for alleviating the spatiotemporal mismatch between energy supply and demand, yet crystallization-induced blockage remains a critical barrier to their practical application. Clarifying the crystallization behavior of molten salts under thermal management conditions is therefore essential for reducing blockage risks and improving thermal storage efficiency. Here, we employed the single hot thermocouple technique (SHTT) to visually investigate the crystallization behavior under constant cooling and isothermal conditions, focusing on crystal incubation time, morphology evolution, growth rates, and their relationship with blockage formation. Results show that under constant cooling conditions, crystallization occurred when the temperature decreased to approximately 454 °C, and the crystal growth rate increased continuously with larger cooling rate; Under isothermal conditions, crystallization was mainly characterized by acicular growth in low-temperature region and particle-aggregation-driven growth in high-temperature region, and the crystallinity decreased to a minimum of 10.8% at 475 °C. In addition, preliminary correlations between temperature parameters and crystallization characteristics were established to provide theoretical support for solving crystallization blockage problems.