Study Of Preparation Of Submicron Ammonium Perchlorate

With the development of solid propellant technology, it is required to meet the requirement of high burning speed. It is generally known that the burning rate of solid propellants increases with the decreasing mean diameter of the AP particle. Therefore, the high burning rate is obtained by the use of mean particle diameter of lμm or less AP oxidant. In this paper, sub-micrometer AP was prepared by solvent-nonsolvent method. The precipitation temperature, stirring intensity, solution concentration and other parameters were discussed to reveal the influence of these factors on the particle size and the yield of AP crystallization. And the ultra-fine AP products were characterized. The main conclusions were as follows:(1) AP was recrystallized through industrial grade coarse powder by solvent-nonsolvent method. The best experimental conditions were:NMP or DMF as solvent, dichloromethane as nonsolvent, lecithin as surfactant, saturated AP solution in room temperature, lmL/min dropping speed and1000rpm rotating rate. The particle size (d5o) of final AP products were0.69μm and1.07μm respectively.(2) The AP products were characterized by TEM and SEM. The results showed that the surface of superfine AP was smooth and ellipsoidal without defects. Meanwhile, the AP products were tested by XRD and FTIR. The results indicated that the physical phase of recrystallization superfine AP scarcely changed compared with raw material.(3) The thermal decomposition of AP was investigated by TG and DSC. The results indicated that there was a significant difference between the thermal decomposition process of large and small particle size AP. The large particle AP had two decomposition processes in high and low temperature range. The sub-micro size AP only had one decomposition process in high temperature range. However, the different particle size of AP shared one endothermic peak of crystal transition at about246℃.(4) The impact sensitivity was investigated in detail. The results showed that the impact sensitivity of AP product increased with the reduction of particle size (d50).The impact sensitivity of sub-micrometer AP increased dramatically compared with industrial coarse AP.