Influence of Vacancy Defects of the Calcium Oxide Surface on the Nonequilibrium Phase Transition of Alkali Metal Salts

Abstract

Molten alkali metal salt effectively promotes the performance of calcium looping (CaL). Deep insight into the nonequilibrium phase-transition characteristic of alkali metal salt is better for the control of the temperature in CaL, which not only ensures the complete melting of metal salt but also prevents the reaction from inhibiting caused by higher temperatures. In this work, therefore, the molecular dynamics simulation method is used to explore the nonequilibrium phase-transition characteristic of Na 2 SO 4 . The results show that the equilibrium melting temperature of nanosodium sulfate on the calcium oxide surface is 810 K, which is lower than the macroscopic melting temperature. Meanwhile, the high heating rates led to the atoms in Na 2 SO 4 unable to break through the thermal stability limit, resulting in overheating of the crystal. Both the surface premelting and overheating melting temperature of the crystal are increased. When the heating rates are 0.25, 0.5, and 1.0 K/ps, the overheating melting temperatures are 845, 885, and 930 K, respectively. More than that, the surface defects enhance the interaction between CaO and Na 2 SO 4 because of the surface being charged. The increases in the interaction not only effectively break the stability of the crystal lattice of Na 2 SO 4 on the defective surfaces but also promote the energy transport inside Na 2 SO 4 . Therefore, as the defect concentration increases from 0 to 3% and 5%, the overheating melting temperature of Na 2 SO 4 gradually decreases from 845 to 836 and 815 K.

Surfactant-Capped Silver-Doped Calcium Oxide Nanocomposite: Efficient Sorbents for Rapid Lithium Uptake and Recovery from Aqueous Media

“…This is because the point defects present both in the bulk and on the surface of CaO strongly determine the surface functionalities of CaO. Furthermore, Chen and co-workers recently studied the non-equilibrium phase transition properties of alkali metal salt above the surface of CaO and analyzed the influence of the surface properties of CaO and the heating rate on the phase transition [61]. In this study, it was shown that surface defects within CaO effectively enhanced the interaction between CaO and the alkali metal salt.…”

On the exploration of the melting behavior of metallic compounds and solid solutions via multiple classical molecular dynamics approaches: application to Al-based systems

“…47,48,55 The defect method works by creating perfect lattices and introducing defects to mechanically destabilize the solid structure. [56][57][58] The interface method is based on the creation of a solid/liquid interface. This interface progresses toward either the solid or the liquid region depending on the imposed equilibrium conditions.…”

Exploring the Challenges of Calcium Looping Integrated with Methane Bireforming for Enhanced Carbon Capture and Utilization

“…Among the various CCU technologies, calcium looping (CaL) has emerged as one of the most prominent techniques. Calcium looping utilizes the reversible reaction between calcium oxide (CaO) and CO 2 , enabling the cyclic capture and release of CO 2 – CaO ( s ) + CO 2 ( g ) ↔ CaCO 3 ( s ) …”