Experimental Investigation of the Thermal Decomposition Pathways and Kinetics of TATB by Isotopic Substitution

Abstract

Real-time measurements of the product gases arising from the thermal decomposition of triamino-trinitro benzene (TATB), its deuterated analogue, and plastically bonded TATB (LX-17) are presented in this study. Gas-phase decomposition products are identified by IR absorption spectroscopy. The frequency shifts in rovibrational spectra due to isotopic substitution and the change in rate of formation of decomposition products due to the kinetic-isotope-effect (KIE) help elucidate the decomposition pathways. The formation of H 2 O precedes other molecules (e. g., HCN, HNCO) during decomposition. After the concentrations of HCN and HNCO molecules reach a peak, their amounts gradually decrease. The concentrations of the other decomposition products (e. g., NH 3 and CO 2 ) rapidly rise after an induction period, which is attributed to the presence of autocatalytic reactions. The trends of chemical evo-lution are similar for all the samples, but their kinetic behaviors are different. This indicates the rates of consistent pathways are changed during thermal decomposition. The kinetics of deuterated TATB decomposition is slower than that of unsubstituted TATB due to the KIE (k H /k D~1 .41). The rate of LX-17 decomposition is slightly lower than unsubstituted TATB (k TATB /k LX-17~1 .15). The KIE is more pronounced during the early stage of decomposition, which is attributed to the first steps of TATB decomposition involving water formation (i. e., H vs D transfer). The KIE slows down the formation of all gases, including those lacking hydrogen (e. g., CO 2 ). These results suggest the TATB thermal decomposition mechanism might involve a series of pathways rather than a set of independent and parallel reactions.

Vibrational Spectra of HNIW and its Isotopologues: A Combined Experimental and Computational Study

“…Reported here are the theoretically predicted vibrational spectra of HNIW and its 2 H, 13 C, 15 N (all), 15 N (nitro), and 18 O isotopologues as well as the experimental Raman and FTIR/ ATR spectra of HNIW and 15 N nitro À HNIW. The calculated isotopic frequency shifts for HNIW and 15 N nitro À HNIW show good agreement with the experimental frequency shifts determined from Raman spectra, with a À NO 2 asymmetric stretching frequency shift of ~36.5 cm À 1 vs. 35.7 cm À 1 , re-spectively.…”

“…Although many experimental and computational works have investigated the vibrational spectrum of HNIW [20][21][22][23][24][25][26], there is still a dearth of information regarding isotopic substitutions. Therefore, to aid in the characterization of any isotopically labeled HNIW variants, the vibrational spectra of the deuterated ( 2 H), 13 C, 15 N (all), 15 N (nitro groups), and 18 O isotopologues have been theoretically predicted in the gas phase. These results are compared to experimentally measured IR and Raman spectra of both unsubstituted HNIW and 15 N-labeled HNIW in which the six nitro groups were synthetically tagged with 15 N atoms (herein referred to as 15 N nitro À HNIW).…”

Probing the Structural Effects of Hydrogen Bonding in 1,3,5-Triamino-2,4,6-trinitrobenzene (TATB): Experimental Evidence by 15N NMR Spectroscopy

“…The data show all the major 15 N features correspond to a set of 1 H resonances centered about δ H = 11 ppm. Previous 1 H NMR spectra collected of TATB produced a single broad resonance at 11.5 ppm Table shows the 15 N­{ 1 H} HetCor data indicating all resonances identified in the spectrum correspond to the single 1 H resonance centered at 11 ppm.…”

“…The spectra were collected using a Revolution NMR HX probe at a spinning rate of 15 kHz. Given the long 1 H T 1 (230 s) previously observed for TATB, 28 the 15 N{ 1 H} cross-polarization magic angle spinning (CP/ MAS) and 15 N{ 1 H} frequency switched Lee−Goldberg heteronuclear correlation (FSLG-HetCor) spectra were collected with a 60 s pulse delay using a 90°1H (1.75 μs) flip-back pulse. 29 A 100 kHz radio frequency (r.f.)…”

“…Previous 1 H NMR spectra collected of TATB produced a single broad resonance at 11.5 ppm. 28 Table 2 shows the 15 N{ 1 H} HetCor data indicating all resonances identified in the spectrum correspond to the single 1 H resonance centered at 11 ppm. A sloping upward shift observed in the spectrum is attributed to the effects of asymmetric bulk magnetic susceptibility.…”