Phase Equilibrium and Thermodynamics Studies on Dissolving Processes of Energetic Compounds: A Brief Review

Crystallization engineering as one of the most typical modification technologies for energetic materials (EMs) has attracted more and more attention due to its facileness and cost-effectiveness. As preliminary and basic research, dissolution thermodynamics is of great significance for crystal quality control during the crystallization process, from which information on the dependence of the solubility on temperature, the metastable zone width, ternary phase diagrams, and thermodynamic parameters can be obtained. The solvent type, solution concentration, temperature, as well as crystallization method could be determined, which are crucial and fundamental factors affecting the crystal habit and structure of EMs. This review focuses on the recent advances on studies of the solid-liquid equilibrium, solubility measurements, correlation of solubility data via different empirical/semiempirical models, calculation of thermodynamic parameters of pure EMs, energetic cocrystals, and some novel energetic compounds and salts as typical examples. This review is narrated based on the diverse solvent systems, such as pure/binary organic solvents, ionic liquids, supercritical fluids, acid/alkaline solutions, and melting systems, based on which further research directions are proposed. This short review on the dissolution thermodynamics of EMs aims to provide researchers with meaningful information on the reliable implementation of crystallization experiments for desired crystal morphologies and structures.