THERMAL-DECOMPOSITION OF ENERGETIC MATERIALS .58. CHEMISTRY OF AMMONIUM-NITRATE AND AMMONIUM DINITRAMIDE NEAR THE BURNING SURFACE-TEMPERATURE

The rapid pyrolysis chemistry of films of ammonium nitrate (AN), NH4NO3, and ammonium dinitramide (ADN), NH4 [N(NO2)2], at temperatures approximating a burning surface is described by the use of T-jump/Fourier transform infrared (FTIR) spectroscopy. The sequence of appearance and amounts of each gas product combined with the net endothermicity and exothermicity of the process at each time enables consistent reaction schemes to be developed. The decomposition of the condensed phase of AN is net endothermic up to at least 33 atm. Although dissociative sublimation and the formation of N2O and H2O dominate the overall process, the superposition of two additional reactions is needed to account for all of the products observed from AN. ADN becomes highly exothermic very early in the decomposition process. The superposition of two stoichiometric reaction branches explains this behavior. The spectra and thermal responses are consistent with the reaction of NH3, with NO2 being the major source of heat released during the decomposition of AN above 33 atm and ADN at 1 atm and higher.