In the case of explosives,product quality,including properties such as performance and insensitivity,can be significantly influenced by particle morphology and particle size [1].Attempts have been made to change the end product properties such as crystal phase,particle size,particle size distribution,and morphology.In general,grinding and crystallization from solution are largely used as micronization processes for explosives in industry.However,these processes have some limitations: It is not only difficult to control morphology and particle size of explosives,but also dangerous to prepare fine particles because of their vulnerability to heat and impact.Therefore,interest has increased in developing technologies that allow the production of micrometer-sized explosives with controlled morphology,crystal phase,and particle size distribution [2].Supercritical fluid processes have gained great attention as a new and environmentally-benign method of preparing the micro-particles of energetic materials [3,4].In this work,RDX (cyclotrimethylenetrinitramine) and HNS (hexanitrostilbene) was selected as target energetic materials [5].The micro-particles formation of energetic materials using supercritical anti-solvent (SAS) recrystallization process was performed and the effect of spraying method on the size and morphology of prepared particles was observed.N,N-Dimethylformamide (DMF) and N-methylpyrrolidone (NMP) were used as organic solvents for dissolving the energetic materials.A spraying tube tip nozzle with an inside diameter of 0.0006 inches and a length of 10 ~ 20 mm was installed into the end of a feed line of solution of an energetic material in order to make a pressure difference between the solution phase and the CO2 phase during spraying the solution into the CO2 phase.The pressure difference was controlled in the range of 0 to 100 bar by changing the length of the spraying nozzle.A big pressure difference generated between CO2 phase and solvent phase during the spraying of solution of the energetic material into CO2 phase could produce the particles with better quality.Specifically,the RDX particles of uniform and spherical shape with the average size of less than 5 μm were obtained at the pressure difference of about 100 bar.The HNS particles recrystallized through our experiments showed the values of the specific surface area in the range of 8 to 12 m2/g,which satisfied the military specification of HNS material.