A combined experimental and theoretical study of the thermal decomposition mechanism and kinetics of ammonium dinitramide (ADN)
An overall decomposition mechanism of ammonium dinitramide (ADN) in the gas phase via density functional theory (DFT) calculations was studied in the present work. Thermogravimetry-Fourier transform infrared (TG-FTIR) and thermogravimetry-mass spectrometer (TG-MS) techniques were used to verify the calculation results. In the thermal decomposition of gaseous ADN (ADN(g)), ADN(g) firstly decomposed into dinitraminic acid (HDN) and NH3, followed by HDN decomposed into other products with small molecular. HDN is found to isomerize into five isomers (HDN-1-5) in the gas phase. For the initial decomposition of HDN, the favorable decomposition pathway of HDN-4 (a structure of HON(O)NNO2) is more likely to form HNO3 and N2O with a huge release of energy (approximately 45 kcal/mol). Meanwhile, product HNO3 and NH3 can firstly combine to form NH4NO3. Both calculated and experimental results indicate that product N2O is firstly formed in the thermal decomposition of ADN(g). Moreover, the formation mechanism and kinetics of other products (NH3, H2O, NO, N2O, NO2, HONO, HNO3, etc.) are also studied and proposed in the thermal decomposition of gaseous ADN. Overall, the systematic mechanistic investigations have provided new and detailed insights on mechanism and kinetics of the thermal decomposition of gaseous ADN, as well as informative factors to further improve the experimental performances and sure be beneficial to other energetic materials synthesis.