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Racoveanu, Ana

Publications and source records attributed to Racoveanu, Ana.

5 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

New thermal decomposition pathway for TATB

Abstract Understanding the thermal decomposition behavior of TATB (1,3,5-triamino-2,4,6-trinitrobenzene) is a major focus in energetic materials research because of safety issues. Previous research and modelling efforts have suggested benzo-monofurazan condensation producing H 2 O is the initiating decomposition step. However, early evolving CO 2 (m/z 44) along with H 2 O (m/z 18) evolution have been observed by mass spectrometric monitoring of head-space gases in both constant heating rate and isothermal decomposition studies. The source of the CO 2 has not been explained, until now. With the recent successful synthesis of 13 C 6 -TATB ( 13 C incorporated into the benzene ring), the same experiments have been used to show the source of the CO 2 is the early breakdown of the TATB ring, not adventitious C from impurities and/or adsorbed CO 2 . A shift in mass m/z 44 (CO 2 ) to m/z 45 is observed throughout the decomposition process indicating the isotopically labeled 13 C ring breakdown occurs at the onset of thermal decomposition along with furazan formation. Partially labeled (N 18 O 2 ) 3 -TATB confirms at least some of the oxygen comes from the nitro-groups. This finding has a significant bearing on decomposition computational models for prediction of energy release and deflagration to detonation transitions, with respect to conditions which currently do not recognize this oxidation step.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Syntheses and characterization of isotopically labeled 1,3,5-triamino-2,4,6-trinitrobenzene (TATB)

Synthesis and characterization of chemical analogues of TATB, where specific atoms in the structure have been isotopically substituted, are reported. 15 N, 2 H, and 18 O have replaced the naturally occurring isotope distributions in the amino and/or the nitro attendant sites and 13 C has replaced the carbon in the ring structure. A modified wet-amination method was used to produce the analogues, and the isotopic replacements were performed by selective choice of labeled precursors. Four 15 N-labeled compounds (N replaced in the amino and nitro positions), two deuterium-labeled compounds (hydrogens replaced on the amino groups), and one 13 C-labeled compound (C in the ring substituted) were synthesized of high isotopic and chemical purity. One partially labeled 18 O-labeled compound (O in the nitro position) was a result of incomplete labeling due to exchange reactions during synthesis. The compounds were characterized by various spectroscopic methods – mass spectrometry (MS), solid-state nuclear magnetic resonance (SS-NMR), infrared (FTIR), powder x-ray diffraction (PXRD), and differential scanning calorimetry (DSC), depending upon the substitution. In conclusion, these compounds have been critical to the efforts in understanding the decomposition pathways of TATB when exposed to abnormal thermal environments.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Comparative analysis of sublimation and thermal decomposition of TATB

This experimental study investigated the effects of confinement, starting mass, and heating rate on TATB thermal decomposition and sublimation using a combined Thermo-Gravimetric Analyzer and Differential Scanning Calorimetry (TGA/DSC) instrument. The confinement of volatile products was varied using different pinhole sizes with TGA/DSC pans. The measurements showed the open pan experiments without lids/pinholes resulted in complete sublimation of TATB between 320 °C and 360 °C. The heat of sublimation was determined to be 176 kJ/mol (42 kcal /mol), consistent with literature data obtained from other experimental techniques. The use of pinholes suppressed the sublimation of TATB such that the decrease in pinhole size resulted in 1) an increase in the enthalpy of reaction and an increase in the amount of carbonaceous material remaining at the end of decomposition, and 2) convergence of the two peak temperatures corresponding to maximum heat flow and maximum weight loss. Also, a transition from a two-exotherm thermal decomposition behavior towards a single-exotherm occurred as the pinhole size was decreased for a given starting mass or as the starting mass was increased for a given pinhole size. These results indicate the kinetics of TATB sublimation, TATB thermal decomposition, and gas diffusion out of a TGA/DSC pan can all compete and result in significantly different enthalpies, amounts of remaining materials, and peak temperatures depending on the pinhole size and starting mass used in the measurements. Furthermore, the results also indicate precise control of process variables (pinhole size, starting mass, and heating rate) in TGA/DSC measurements is required for thermal safety assessment of explosives.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗