Preparation Of Submicronmeter-sized AP By Mechanical Pulverization Method And Its Performance Study

Ammonium perchlorate (AP) is the most common energetic material that is widely used as an oxidizer in composite solid propellants. Recent studies have shown that the burning rate of solid propellant increase with the decrease of the particle size of AP. The burning rate of propellant would increased significantly when we reduced the particle size of oxidizer agent to submicro level.However,the existing methods for preparation of submicron AP was hardly to satisfy the requirement of the solid propellant charge. This paper mainly studied the preparation of submicron AP by mechanical pulverization and also studied the properties of the produced AP,such as the chemical purity,crystalline structure, mechanical sensitivities, the thermal decomposition performance and so on. The main results are showed as follows:(1) The optimum technological conditions for producing submicronmeter-sized AP by variable-controlling approach have been obtained:the grinding media ball was zirconia balls with a diameter of 0.6 mm, sec-butyl alcohol as dispersion medium,the grinding speed and time was 1000rpm and 7 hours, respectively. The slurry concentration was 10% and the ball material ratio was 100.The particle size(d50) of final AP products was 0.46μm,(d50) was 0.99μm.(2) FT-IR、XPS as well as XRD were employed to character submicron AP. The results showed that the prepared sub-micron AP was spherical and no mpurities contain in the crystal, and the crystal structure did not changed. The mechanical sensitivity of AP increases with the reduction of particle size.Compared with raw AP, the impact sensitivity and fricti of submicron AP increased by 18.7% and 30%, respectively.The high-temperature decomposition peak temperature of submicron AP was advanced 60.1℃, the heat release increased 289J/g and the activation energy(Ea) reduced by 26.7 KJ·mol-1. The reasons of these changes with the grain size of AP was analyzed.(3) The effects of aluminium on the thermal decomposition of AP process were studied.The addation of aluminum powder can lower the high temperature decomposition of submicron AP, while showed an opposite effect on the low temperature decomposition process.The heat release of AP decreased with the increase of aluminium content in certain degree.The smaller the grain size of AP,the greater the heat quantity was. The heat quantity of submicronmeter-sized AP was obviously higher than micron grade AP.(4) The catalytic properties of K3Co(NO2)6、CuCr2O4 and CuO on the thermal decomposition of AP were investigated. The high-temperature decomposition peak temperature of AP was advanced and the heat release increased.The catalytic effect of K3Co(NO2)6 was better than CuCr2O4 and CuO and the submicron AP with the best catalytic performance.With the addation of K3Co(NO2)6, the high-temperature decomposition peak temperature of submicron AP was advanced 60.5℃ and the heat release was increased by 72.7%. At the same time, its catalytic mechanism was also been investigated.