Novel utilization of the molecular band signal in metal oxides: understanding the aging process of pyrotechnic substances by using laser induced plasma emissions

Abstract

Laser-induced breakdown spectroscopy (LIBS), commonly used for atomic emission analysis, was used to gain some understanding of the process of aging in metalized pyrotechnic substances. In particular, the formation of zirconium dioxide (ZrO2) was investigated through the ZrO molecular band structure. The plasma emission structure that considers the electronic, vibrational and rotational transitions in molecules corresponds to the ZrO α (1,0) bands of the b3ϕ – a3Δ system. The ZrO signal originates from both pure Zr exposed to oxygen, as well as from pre-existing ZrO2, which makes it difficult to discriminate its source. Here, we confirmed that the aging samples showed the same increase in the ZrO signal as the non-aging samples with added ZrO2. A calibration curve for varying ZrO2 concentration with respect to the area under curve (AUC) of the ZrO signal intensity was constructed. The percentage of oxidation in two types of metalized pyrotechnic substances, namely Zr/KClO4 and Zr/Fe2O3, was predicted through the geometrical interpretation of the ZrO molecular emission spectra.