The thermal decomposition of the new energetic material ammoniumdinitramide (NH4N(NO2)2) in relation to Nitramide (NH2NO2) and NH4NO3

This qualitative study examines the response of the novel energetic material ammonium dinitramide (ADN), NH₄N(NO₂)₂, to thermal stress under low heating rate conditions in a new experimental apparatus. It involved a combination of residual gas mass spectrometry and FTIR absorption spectroscopy of a thin cryogenic condensate film resulting from deposition of ADN pyrolysis products on a KCl window. The results of ADN pyrolysis were compared under similar conditions with the behavior of NH₄NO₃ and NH₂NO₂ (nitramide), which served as reference materials. NH₄NO₃ decomposes into HNO₃ and NH₃ at 182°C and is regenerated on the cold cryostat surface. HNO₃ undergoes presumably heterogeneous loss to a minor extent such that the condensed film of NH₄NO₃ contains occluded NH₃. Nitramide undergoes efficient heterogeneous decomposition to N₂O and H₂O even at ambient temperature so that pyrolysis experiments at higher temperatures were not possible. However, the presence of nitramide can be monitored by mass spectrometry at its molecular ion (m/? 62). ADN pyrolysis is dominated by decomposition into NH₃ and HN(NO₂)₂ (HDN) in analogy to NH₄NO₃, with a maximum rate of decomposition under our conditions at approximately 155°C. The two vapor phase components regenerate ADN on the cold cryostat surface in addition to deposition of the pure acid HDN and H₂O. Condensed phase HDN is found to be stable for indefinite periods of time at ambient temperature and vacuum conditions, whereas fast heterogeneous decomposition of HDN at higher temperature leads to N₂O and HNO₃. The HNO₃ then undergoes fast (heterogeneous) decomposition in some experiments. Gas phase HDN also undergoes fast heterogeneous decomposition to NO and other products, probably on the internal surface (ca. 60°C) of the vacuum chamber before mass spectrometric detection. © 1993 John Wiley & Sons, Inc.