Abstract
Ammonium perchlorate (AP) is a common oxidant in solid propellants, and its thermal decomposition characteristics at low temperatures (less than 240 °C) are key to the study of the thermal safety of propellants. Here, the low-temperature thermal decomposition characteristics of AP were investigated at 230 °C. The micromorphology of the low-temperature decomposition residues was characterized by scanning electron microscopy and 3D nano-computed tomography in order to analyse the evolution of microscopic pore structures, and the effect of the AP pore structure on combustion performance was then tested and analysed with a homemade closed bomb. The results demonstrate that the low-temperature decomposition of AP first occurs near the surface of the particles, simultaneously starting at multiple points and forming pores, and then gradually expands towards the interior until almost all of the pores connect with one other. Compared with ordinary AP, porous AP has a significantly improved combustion rate. When the ratio of porous AP to Al was 80:20, the peak pressure in the closed bomb was increased by 2.7 times; the rate of change in peak pressure increased 34 times, leading to a higher reaction speed and higher reaction intensity, and a typical explosion reaction occurred.
Highlights
Solid propellant charges are prone to burning or exploding under unexpected thermal stimulation, leading to catastrophic accidents [1,2]
As the decomposition continued and the mass loss reached 20.2% (b), the pores had spread to the centre of the particles, with most pores being connected, pores had spread to the centre of the particles, with most pores being connected, a few pores were still locally connected
Rapid decomposition and slow reaction at 230 C, which is the temperature for the slow80:20 cook-off of the1.34 propellant
Summary
Solid propellant charges are prone to burning or exploding under unexpected thermal stimulation, leading to catastrophic accidents [1,2]. Only by understanding the evolution of pores during the low-temperature decomposition of AP particles can we further analyse the effect of the low-temperature decomposition of AP on the thermal safety of propellants. To better explore the decomposition of AP particles at low temperature and its influence on the thermal safety of propellant, it is necessary to quantitatively study the microstructure evolution of AP particles and the effect of the pore structure on combustion properties during low-temperature thermal decomposition. The effect of porous AP on combustion performance was studied by using a closed bomb, and the response mechanism of the composite propellant under slow cook-off conditions was analysed
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