Sensitivity of a high explosive like RDX (cyclotrimethylenetrinitramine) depends largely on its particulate properties such as the particle sizes,size distributions,morphologies,solvent inclusions,and defects.Size reduction is one of the most effective ways to obtain insensitive explosives while keeping their performance moderate or even better.Although physical processes such as milling or grinding are often used in micronization processes,certain limitations like wide size distribution,rough surfaces,and friction exist.To overcome these limitations,crystallization using organic solvents is widely used to produce the desired explosive particles.Supercritical fluid crystallization processes are of importance because of the special characteristics of supercritical fluids such as high diffusivity,liquid-like solvent power,and controllable density.By the compression and expansion of the supercritical fluid,the solvent power of the fluid can be controlled,thereby giving useful properties in crystallization processes.In this study,RDX particles were obtained by a Supercritical Anti-Solvent (SAS) process.RDX was initially dissolved in an organic solvent which is sprayed into a flowing medium of supercritical carbon dioxide,where the extraction of the organic solvent leaves RDX to precipitate into micro particles.The important parameters in this process were found to be the solvent,temperature,pressure,and solution flow rate.It was found that using acetone as the solvent,the obtained particles were smaller and more spherical-like at relatively high temperature and low pressure.