Study on the Aging Mechanism of Boron Potassium Nitrate (BKNO3) for Sustainable Efficiency in Pyrotechnic Mechanical Devices

The aging of propellants in PMDs is considered to be one of the primary factors affecting the performance of PMDs. Thus, studies on the aging mechanism of propellants, which have not yet been addressed extensively, pose a solution to securing the sustainable operation of PMDs. We characterized one of the most commonly used commercial propellants (boron potassium nitrate (BKNO3)) and investigated its aging mechanism rigorously. Based on thermal analyses, we demonstrate that the decomposition of laminac, a polymer binder, is the fastest spontaneous reaction. However, it will not self-initiate at a storage temperature as high as 120 °C. The effect of the humidity level was examined by characterizing BKNO3 samples prepared. The heat of reaction and the reaction rate decreased by 18% and 67% over 16 weeks of aging, respectively. This is attributed to the oxide shells on the surface of boron particles. The formation of oxide shells could be confirmed using X-ray photoelectron spectroscopy and transmission electron microscopy–energy dispersive spectroscopy. In conclusion, surface oxide formation with the aging of BKNO3 will decrease its propulsive efficiency; oxidation reduces the potential energy of the system and the resulting oxide decreases the reaction rate.