Mass spectrometric study of the thermal decomposition of ammonium perchlorate

Abstract: This review represents an attempt to summarize literature data on thermal decomposition of ammonium perchlorate. The mechanism of thermal decomposition and various factors which influence on the thermal decomposition of ammonium perchlorate are discussed.

Abstract: The thermal decomposition of ammonium perchlorate has been studied using thermogravimetric analysis (TGA), coupled with Fourier transform infrared (FTIR) spectroscopy and electron ionization (EI) mass spectrometry (MS) of the evolved gases. The thermal decomposition could be demarcated into three distinct regimes, the low temperature decomposition (LTD) regime and the high temperature decomposition (HTD) regime, with an intermediate regime between the two, named as the intermediate temperature decomposition (ITD) regime. Using FTIR spectroscopy, N 2 O was detected as the primary species during the LTD regime, followed by HCl, NO 2 , and HNO 3 , in lesser quantities. On the contrary, NO 2 was found to be the principal species, followed by almost equal concentrations of HCl, N 2 O, and HNO 3 in the HTD regime. Other important species, such as H 2 O, Cl 2 , O 2 , etc., although observed by MS, were not quantified. NO could not be identified in appreciable quantities in any of the regimes. Based on the species detected during the present work, and previous research, a reaction scheme has been proposed for AP decomposition in the LTD and the HTD regimes.

Abstract: The application of transition metal oxides as catalyst for many industrial processes is long known and many of them are often employed as thermal decomposition/combustion catalyst for composite solid propellants. The focus in this study is on investigating the catalytic effect of copper oxide (CuO) nanorods on the decomposition mechanism and kinetic behaviour of composite solid propellant. Thermal-kinetic evaluations of the catalysed and non-catalysed composite propellant were carried out by a model free (non-linear integral isoconversional) and a model fitting (Coats–Redfern) method. The CuO nanocatalyst was synthesised by the hydrothermal method, characterised by high resolution transmission electron microscope, selected area electron diffraction and powder x-ray diffraction and used as a catalyst in the propellant formulations. Thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) have been used to identify the changes in the thermal and kinetic behaviour of the catalysed composite propellant. The different stages of decomposition were separated and the influence of catalyst on each decomposition stage of the propellant is investigated. The major effect of the catalyst was observed in the oxidation of sublimation products stage or second stage decomposition of the oxidiser (ammonium perchlorate). The model fitting analysis of this stage suggested a change in three dimensional diffusion (D3) model to the Avrami–Erofeev model by the addition of the nanocatalyst. Furthermore, the model free method suggested a decrease in the activation energy by the addition of nanocatalyst. The dependence of activation energy on the extent of conversion was used to draw mechanistic conclusions about the catalytic activity of CuO nanorods on the composite solid propellant.

Abstract: The topokinetical aspects of the low-temperature decomposition (LTD) of ammonium perchlorate (AP) crystals, i.e., the nucleation rate ( V n ), the rate of nuclei growth ( V g ) and their dependence on the concentration of some additives and the temperature, have been investigated. On the basis of experimental data obtained, it is inferred that the nucleation rate of the LTD for chemically pure AP is determined by the content of free protons and unavoidable ClO − 3 ion impurity and has the activation energy E n = 70 ±4 kcal mole −1 . The length of the induction period of nucleation (τ n ) is a function of ClO − 3 The corresponding value of the effective activation energy is E τ = 22 ±5 kcal mole −1 . Addition of proton donors catalyzets the nucleation process; proton acceptors inhibit it, but all the proton active additives insignificantly influence the value of V g . A mechanism of the nucleation process is suggested. Based on this mechanism it is possible to explain in a consistent way all the experimental data obtained and the well-known phenomenon of incomplete (30%) decomposition of AP characteristic of LTD. During UV irradiation of AP crystals through an opaque stencil, a latent photographic image of the stencil arises within the bulk of the AP. In the early stages of the LTD, this image may be developed. It is supposed that the latent image arises due to the generation of photo-induced ClO − 3 ions in the course of UV irradiation. On the basis of all available experimental data as well as the proposed mechanism of LTD, a means of nonempirical regulation of AP stability is suggested. In conclusion, the unresolved problems concerning the LTD of AP are reviewed.