Preparation of fine powders by clathrate-forming freeze-drying: a case study of ammonium nitrate

摘要

Fine powders of ammonium nitrate were prepared by the freeze-drying of a solution in a THF-water mixture. Freezing gives a THF hydrate and dispersed ammonium nitrate particles; the THF hydrate can be then removed by sublimation to leave fine ammonium nitrate powder. To optimize the process, the stability of cubic structure II THF clathrate hydrate in the presence of ammonium nitrate was studied by X-ray diffraction and thermal analysis.