Towards a Deep Insight Into Thermal and Moisture Aging of Silicon‐Based Pyrotechnic Delay Composition Through a Combination of Spectroscopic Techniques – Principal Component Analysis Approaches

Abstract

AbstractThe aging of pyrotechnics is heavily influenced by temperature and humidity during their long‐term storage. The investigation of the aging mechanisms of such composites is of great interest for their safe storage and use in weapon systems, hence avoiding any unexpected phenomenon or decrease in performance. This study is aimed at understanding the aging effects related to temperature and moisture on pyrotechnic delays composed of silicon as fuel and lead oxide (Pb3O4) and barium chromate (BaCrO4) as oxidizers. The aged samples were considered for spectroscopic analysis using Fourier transformed infrared spectroscopy (FTIR), Raman spectroscopy, X‐ray diffraction spectroscopy (XRD), and surface morphology analysis using scanning electron microscopy (SEM). The results obtained showed that temperature and moisture induce distinct structural and morphological modifications on the composition. The thermal aging causes thermal decomposition of the lead oxide, followed by the oxidation of the fuel particles to form silicon dioxide (SiO2). On the other hand, under moisture, the lead oxide is stable and does not participate in the aging process and the barium chromate is converted to chromium oxide molecules Cr2O3. At the same time, Si is oxidized to SiO2 and orthosilicic acid Si(OH)4 in the presence of humidity. The SEM images revealed that the surface of the aged samples tended to be rough in addition to the formation of surface cracks. At low aging periods of 20, 40, and 60 days, no chemical alterations have been noticed, whereas, beyond 80 days, the changes become more apparent. By coupling the above analytical techniques with principal component analysis (PCA), it was possible to accurately differentiate the aged samples according to their aging time and to detect any compositional change within the powder even at low aging periods.