Ammonium Dinitramide:  Kinetics and Mechanism of Thermal Decomposition

Thermal decomposition of ammonium dinitramide (ADN) has been studied by differential scanning calorimetry (DSC) and thermal gravimetry combined with mass spectrometry (TG−MS). ADN decomposes in the range 130−230 °C with an overall heat release of 240 ± 40 kJ mol -1 . The product gases have been identified by MS as NH 3, H 2 O, NO, N 2 O, NO 2, HONO, and HNO 3 . The global activation energy determined from TG experiments decreases from 175 ± 20 kJ mol -1 at the beginning of the reaction to 125 ± 20 kJ mol -1 when the reaction is near completion. Experiments conducted at different carrier gas flow rates indicate that the reaction is catalyzed by product gases released during the reaction. A condensed phase ionic reaction mechanism is proposed, in which ammonium nitrate and ammonium mononitramide (NH 4 NNO 2 ) are formed as intermediates in two competing channels.