A kinetic investigation on the mechanism and activity of copper oxide nanorods on the thermal decomposition of propellants

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.