Abstract: Ultrafine sphere-like ammonium perchlorate (AP) particles are prepared by using an improved jet mill. The morphologies, particle size distributions, sample compositions and molecular structures of raw, ultrafine non-spherical and sphere-like APs are characterized by using scanning electron microscope, micron laser particle size analyzer, Fourier transform infrared spectrometer and X-ray diffractomer. The thermal decomposition, impact sensitivity and friction sensitivity, bulk density, hygroscopicity and caking of ultrafine sphere-like and non-spherical AP particles with same size are measured. The results indicate that the ultrafine AP particles prepared by jet milling method are basically sphere-like with particle size of 2 μm. The AP particles also have the characteristics of uniform particle size, smooth surface without defect, good dispersion and high purity. Compared with non- spherical AP particles with the same size, the thermal stability of sphere-like AP particles is improved slightly, and their impact and friction sensitivities are decreased by 37.6% and 26.7%, respectively; the apparent bulk density is increased by 10.7%, the tap density is increased by 24%；hygroscopicity and caking are effectively improved. Key

Key words: ordnancescienceandtechnology, ammoniumperchlorate, jetmill, sphericization, mechanicalsensitivity, thermaldecompositionperformance, hygroscopicity