Abstract
Pyrotechnic systems can undergo chemical changes during aging that can induce significant performance degradation. The specific attributes determining such thermal degradation are unclear, and thus the present study considers three different pyrotechnic compositions that utilize metal fuels (Tungsten (W), Zirconium (Zr), and Titanium (Ti)) and a common oxidizer (potassium perchlorate (KClO4)). The surface analysis confirms the pre-oxidation of the metals and a-priori decomposition of the oxidizers in the hygrothermally aged samples. The thermal analysis reveals the distinct moisture adsorption per each metal fuel and the reduction in the heat of reaction. Both Ti-based (TiH2/KClO4) and Zr-based (Zr/KClO4) compositions having a relatively low covalent bonding strength with the oxygen readily adsorbed moisture even in short aging duration, while W-based composition (W/KClO4/BaCrO4) with high covalent bonding strength required more than ten weeks of aging for the similar moisture adsorption. All cases showed a decreasing heat of reaction with aging, which is associated with this chemical affinity of the respective metal towards the oxygen. Thus, the metal fuel influences the early stage degradation related to the covalent bonding strengths, while the oxidizer determines the thermal stability, responsible for prolonged decompositions. The present results are expected to make predictions about the thermal degradation of aging pyrotechnics that utilize these standard metal elements.
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