Microparticle formation and crystallization rate of HMX with supercriticalCO2 antisolvent recrystallization

Microparticle formation and crystallization rate of 1,3,5,7-tetranitro-1,3, 5,7-tetraazacyclooctane (HMX) in acetone solution using supercritical carbo n dioxide antisolvent (GAS) recrystallization were studied. Scanning electr onic microscopy, X-ray diffraction and infrared radiation were used to exam ine particle size, crystallinity and chemical structure. The results show t hat beta -HMX microparticle in different average size (2-9.5 mum) and with narrow size distribution were obtained by controlling the expansibility, ex pansion speed, initial concentration and temperature during recrystallizati on of HMX. The formation of nuclei may be a main cause of consumption of so lute when the solution is expanded rapidly enough and the equilibrium conce ntration is lower, in which almost monodisperse microparticle can be obtain ed.