LAUSR

The thermal decomposition behaviour of guanidinium nitrate (GN), an energetic material, was analysed using a combined experimental and computational approach. Simultaneous thermogravimetric analysis, Fourier transform infrared spectroscopy and mass spectrometry (TG-FTIR-MS) experiments were carried out at three different heating rates under closed and open crucible conditions. A two-stage decomposition process was observed, and the major gases evolved were found to be NH3, N2O, NO2 and CO2. Quantum mechanics based ab initio computations were performed to evaluate the possible decomposition pathways available for GN. Results indicate that decomposition of GN is not initiated in the condensed phase as the guanidinium cation and the nitrate anion are highly stable. The most likely mechanism involves isomerization of GN followed by a proton transfer in the gas phase to yield nitric acid and guanidine. These products then further react to form nitroguanidine (NQ) and H2O. NQ dissociates via several competing pathways to yield NH3, N2O, H2O and CO2. HNO3 decomposition can help explain NO2 formation. The residue left towards the end of TG can be attributed to dimerization and trimerization reactions of cyanamide.