Science and Technology of Energetic Materials

Vol.76, No.4 (2015)

Research paper

A condensed phase decomposition mechanism for ammonium nitrate
Yu-ichiro Izato and Atsumi Miyake


The purpose of this study was to develop an improved understanding of the condensed phase decomposition mechanism of ammonium nitrate (AN). To this end, the thermal properties of AN were studied using pressurized differential scanning calorimetry (PDSC), and evolved gases were analyzed by combining PDSC with Fourier transform infrared spectroscopy (PDSC-FTIR) and mass spectrometry (PDSC-MS). PDSC results showed that AN undergoes an exothermic reaction above 0.3 MPa, and that this exothermic reaction offsets the endothermic reaction of AN as the ambient pressure is increased. Evolved gas analyses demonstrated that AN generates N2O and H2O during the exotherm and NO2 throughout the endotherm. The heat flow associated with the thermal decomposition of AN was simulated assuming that the decomposition rate of AN is given by -dCAN/dt=109.4exp(-126000/RT)CNH4+CHNO3,that the heat of reaction is 105 kJ as per the reaction equation HNO3(l)+NH4+(l)=N2O(g)+H3O+(l)+H2O(g)+105kJ and that CCH4+ and CHNO3 are constant due to chemical equilibrium. The heat flow curves calculated in this manner are in good agreement with the experimental DSC curves obtained at 1.1 MPa.

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ammonium nitrate, thermal decomposition, condensed phase decomposition, thermal analysis, evolved gas analysis

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