Thermal Decomposition, Ignition and Kinetic Evaluation of Magnesium and Aluminium Fuelled Pyrotechnic Compositions

This paper describes the thermal, kinetic and ignition behaviour of three pyrotechnic mixtures comprising Al + Ba(NO3)2, Mg + NH4ClO4, and Mg + KMnO4. Aluminium (Al) and magnesium (Mg) are metal fuels whereas barium nitrate, potassium permanganate and ammonium perchlorate are oxidants. The main objective of the paper is to assess the safety and relative reactivity of these pyrotechnic combinations. The experimental results indicate that aluminium powder reacts exothermically with the decomposition products of barium nitrate near 601 °C. A similar kind of exothermic reaction takes place between magnesium powder and ammonium perchlorate at 338 °C. Heat flow data obtained from multiple heating rate experiments were used to calculate the kinetic parameters, such as activation energy, reaction rate constant and frequency factor, using the Kissinger method. Critical ignition temperatures of all three compositions have been estimated in order to evaluate their thermal stability. The results show that all of these compositions are thermally stable and their relative reactivity decreases in the following order: Mg + NH4ClO4 > Mg + KMnO4 > Al + Ba(NO3)2.