Thermal, kinetic and morphological studies of available and synthesized pyrotechnic/propellant compositions and their ingredients

Abstract

The work presented in this thesis is focused on the thermal, kinetic and morphological studies of various pyrotechnic/propellant compositions and their ingredients. A lot of research work has been carried out in the field of explosives; however, there is a lack of theoretical understanding and experimental work concerning the reaction kinetics of the pyrotechnics. The published work in the field of pyrotechnics presents some individual studies concerning different aspects such as thermal behaviour, kinetics and aging of the pyrotechnic compositions and their ingredients. The present work is a concerted effort to provide an insight into the thermal behaviour, kinetics, aging and morphological aspects of pyrotechnics/propellants. For this purpose, differential scanning calorimetry, differential thermal analysis and thermogravimetery have been mainly used along with scanning electron microscopy and X-ray diffraction for accomplishment of the present work. The comparison of thermal cum kinetic behaviour of five different oxidizers that are commonly used in various pyrotechnic/propellant compositions was carried out. Next, modified barium nitrate with micro porous structure was synthesized using three different vesicants to make it more reliable as a pyrotechnic oxidant. The pyrotechnic composition formulated with the modified oxidizer ignited at a lower temperature as compared to the one formulated with pure barium nitrate. The ignition behaviour of the vesicant modified barium nitrate has not been reported earlier to the best of our knowledge. Moreover, thermal and kinetic behaviour of ammonium perchlorate has been improved by catalyzing it with a small amount of nano magnesium oxide catalyst. The results indicate that the two distinct decomposition stages of the pure ammonium perchlorate merged with each other and reduced to a single stage. Furthermore, the reaction rate constant of the catalyzed AP also increased significantly. Pyrotechnics and propellants are inherently associated with some potential safety hazards and are therefore required to be investigated for their stability and decomposition kinetics. The thermal, kinetic and ignition behaviour of three pyrotechnic mixtures has been investigated in detail to elucidate the mechanism of ignition of these fuel oxidizer mixtures and to assess the thermal stability and reactivity. Temperature and humidity are amongst the important factors that influence the shelf life and ignition behaviour of the pyrotechnics. The effect of aging on two commonly used military pyrotechnics has been studied. The investigated compositions include SR-524 and SR-562 pyrotechnic compositions. The results indicate that aging of the pyrotechnic compositions at extreme conditions of temperature and humidity changed their thermal behaviour, kinetics, chemical composition and the surface features. The last part of the thesis describes in-depth kinetic analysis of three different versions of the composite solid propellant. Magnesium oxide and zinc oxide nano particles were used as catalysts to alter the performance of the composite propellant. The kinetic analysis has been carried out by Kissinger method, Flynn–Wall–Ozawa method, Friedman method and Kissinger-Akahira-Sunose method. The results indicate lowering of the decomposition temperatures in the catalyzed versions of propellant. The kinetic analysis showed increased reactivity of the catalyzed versions of the propellants. In a nut shell, the work presented in the thesis provided new insight into the thermal, kinetic and morphological aspects of propellants and pyrotechnics vis-a-vis their enhanced reactivity through incorporation of vesicants and nano catalysts, coupled with aging studies, to help design formulations for specific requirements wherever required.