Thermal decomposition of energetic materials 60. Major reaction stages of a simulated burning surface of NH4ClO4

Abstract Major stages of pyrolysis that occur in a heterogeneous gas-condensed phase layer of NH 4 ClO 4 (AP) representative of the burning surface are described. T-Jump/FTIR spectroscopy provides the sequence of appearance of the gas products and the corresponding energy balance of a thin layer of AP heated at 2000°C/s to 440°C under 13 atm Ar. Some HClO 4 , but no NH 3 , escapes the reaction zone before significant heat is released. NH 3 is oxidized to NO 2 , N 2 O, and H 2 O. At least some of the N 2 O may result from 2HNO → N 2 O + H 2 O. As the decomposition rapidly accelerates and becomes strongly exothermic, NO and H 2 O are formed in large amounts and no more HClO 4 is evolved. In agreement with previous kinetic schemes, these observations are consistent with the large influence of HClO 4 + HNO → NO + ClO 3 + H 2 O in the overall rate. The acceleration of the process may result from growth in the HNO concentration. The final product concentrations qualitatively resemble the product profiles determined by microprobe-mass spectrometry of the AP flame. Dynamic weight loss of an AP film determined by SMATCH/FTIR spectroscopy extrapolates reasonably well to the burn rate of AP measured with a combustion bomb.