Particle Size and Crystal habit Modification of Ammonium Perchlorate Using Cooling Sonocrystallization Process

Abstract

Ammonium perchlorate (AP) is a widely used solid oxidizer in solid propellant formulations, with its particle size and crystal habit significantly affecting performance. Since controlling these properties remains challenging, this study employs an intensified crystallization strategy, specifically a cooling sonocrystallization process, to recrystallize AP to control and modify its particle size and crystal habit. The effects of solution concentration, sonication intensity, sonication pulse on/off recipe, and cooling rate on the recrystallization of AP are first investigated using a Taguchi L9 orthogonal array design. By understanding the main effect of these operating parameters, further sonocrystallization experiments are designed for process improvement. Compared with the unprocessed AP, the crystal habit and mean particle size of AP are considerably modified after cooling sonocrystallization, achieving a mean size of approximately 50 µm with a regular habit. Consistency in crystal structure and spectrometric properties between sonocrystallized and unprocessed AP was confirmed. Furthermore, the thermal properties and decomposition behavior of the sonocrystallized AP are analyzed, revealing improved exothermic characteristics. These results prove that cooling sonocrystallization is an efficient tool for producing AP particles and also holds the potential for preparing fine particles of other energetic materials.