An overview on the phase transition of ammonium nitrate

Solid ammonium nitrate (NH4NO3) is widely used in explosives andfertilizers. Since one of these products should explode and the othershould not decompose in an uncontrolled way, researchers in bothindustries have been interested in how this compound can best beproduced, handled, stored, and finally used. All these concerns are mostly related to the phase transitions. Meanwhile, ammonium nitrate is acommon constituent of fine atmospheric aerosols, accounting for 10-30%of aerosol mass. Because of its ubiquity and environmental impacts, the properties of NH4NO3 aerosols have been considered by the atmosphericresearch community. The phase transition of NH4NO3 aerosols is one ofthe most important topics in atmospheric science. Accordingly, the different solid phases of NH4NO3 and the phase transition attract muchinterest of chemists, aerologists and physicists. Under ambient pressure, five stable polymorphic phases of NH4NO3 have been accessed at different temperatures. The different phases of NH4NO3 exhibit different physical and thermodynamic properties such as solubility, specific volume and heat capacity. In this chapter, a detail characterization of the stable polymorphic forms and the phase transitions are presented.