Ignition and combustion behavior of zirconium-based pyrotechnic igniters and pyrotechnic delays under aging

Abstract

Pyrotechnic materials often necessitate high reliability and stability to be utilized in energetic devices. However, prolonged storage of these materials degrades their performance in many ways and results in failure of these devices. Only a few studies have focussed on their burning characteristics, and reported limited understanding on the effect of aging on this behavior of such materials. In this study, ignition and combustion behavior of pyrotechnic materials based on zirconium (Zr) as fuel and potassium perchlorate (KClO4) or iron(III) oxide (Fe2O3) as oxidant are investigated, for various aging conditions. Pristine samples are compared with samples subjected to aging under 91 °C (thermally aged) and seasonal changes (naturally aged). The ignition delay time as a function of maximum wire temperature is obtained through high-speed combustion photography for these samples. Surface features and oxide content are analyzed using scanning electron microscopy and x-ray photoelectron spectroscopy techniques. Results indicate that ignition delay time increases significantly with aging period for both pyrotechnic igniter and pyrotechnic delay samples. However, this time reduces as the maximum wire temperature is increased for all samples. Naturally aged samples exhibit longer ignition delay times and higher metal oxide content when compared to thermally aged ones. Both pre-oxidation of metallic fuel and prior thermal decomposition of oxidizer play an important role in causing this behavior with aged samples.