Comparative Study of Ultraviolet Laser-Based Time-Resolved Photoacoustic Fingerprint Spectra and Thermal Decomposition Mechanisms of Energetic 1,2,3-1H-Triazole Derivatives Under Controlled Pyrolysis

Abstract

We report the comparative study of photoacoustic (PA) fingerprint spectra, thermal decomposition, and stability mechanism of some phenyl and bis series energetic compounds named 1-(2-methoxy,-3,5-dinitrophenyl)-1H-1,2,3-triazole (S₅), 1-(3-methoxy, 2, 6 dinitrophenyl) 1H-1, 2, 3 triazole (S₁₀), 1-(4-nitrophenyl)-1H-1,2,3-triazole (S₈), and 2,6-bis ((4-(nitromethyl)-1H-1,2,3-triazol-1-yl)methyl) pyridine (S₉). Fourth harmonic wavelength, i.e., 266 nm of pulse duration 7 ns and 10 Hz repetition rate obtained from Q-switched Nd: YAG laser, was used to record the thermal PA spectra of these compounds under controlled pyrolysis condition in the range of 30–350 ℃. The PA fingerprint spectra are produced due to entire molecule vapor along with principal functional byproduct NO₂ molecule. NO₂ molecule is a major gas released during thermal decomposition due to weakest nature of C–NO₂ bond. Further, NO₂ molecules are involved in photodissociation process due to π*←n transition and converted into NO molecules inside the PA cell due to excitation by 266 nm wavelength. The combined results of PA and gas chromatography–mass spectrometry (GC-MS) spectra along with thermo gravimetric–differential thermal analysis (TG-DTA) data confirm the thermal decomposition mechanism process that can be completed in multiple steps. In addition, GC-MS spectra also confirm the release of NO and NO₂ molecules. The effect of incident laser energy and data acquisition time has been carried out for understanding the behavior of acoustic modes. Finally, the thermal quality factor “Q” is measured to test the stability of compounds.