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 ma terial ammonium dinitramide (ADN), NH4N(NO2)2, to thermal stress under low heating rate conditions in a new experimental apparatus. It invol ved a combination of residual gas mass spectrometry and FTIR absorptio n spectroscopy of a thin cryogenic condensate film resulting from depo sition of ADN pyrolysis products on a KCl window. The results of ADN p yrolysis were compared under similar conditions with the behavior of N H4NO3 and NH2NO2 (nitramide), which served as reference materials. NH4 NO3 decomposes into HNO3 and NH3 at 182-degrees-C and is regenerated o n the cold cryostat surface. HNO3 undergoes presumably heterogeneous l oss to a minor extent such that the condensed film of NH4NO3 contains occluded NH3. Nitramide undergoes efficient heterogeneous decompositio n to N2O and H2O even at ambient temperature so that pyrolysis experim ents at higher temperatures were not possible. However, the presence o f nitramide can be monitored by mass spectrometry at its molecular ion (m/e 62). ADN pyrolysis is dominated by decomposition into NH3 and HN (NO2)2 (HDN) in analogy to NH4NO3, with a maximum rate of decompositio n under our conditions at approximately 155-degrees-C. The two vapor p hase components regenerate ADN on the cold cryostat surface in additio n to deposition of the pure acid HDN and H2O. Condensed phase HDN is f ound to be stable for indefinite periods of time at ambient temperatur e and vacuum conditions, whereas fast heterogeneous decomposition of H DN at higher temperature leads to N2O and HNO3. The HNO3 then undergoe s fast (heterogeneous) decomposition in some experiments. Gas phase HD N also undergoes fast heterogeneous decomposition to NO and other prod ucts, probably on the internal surface (ca. 60-degrees-C) of the vacuu m chamber before mass spectrometric detection.