Advisory Committee Chair
Yogesh K Vohra
Advisory Committee Members
Tracy P Hamilton
Aaron L Lucius
Nenad Velisavljevic
Sergey Vyazovkin
Document Type
Dissertation
Date of Award
2016
Degree Name by School
Doctor of Philosophy (PhD) College of Arts and Sciences
Abstract
The high pressure-temperature (P-T) phase diagram of 1,1-diamino-2,2-dinitroethylene (FOX-7) was determined by in situ synchrotron infrared radiation spectroscopy and resistively heated diamond anvil cell (DAC) techniques. The stability of the high P-T FOX-7 polymorphs is established from ambient pressure up to 10 GPa and temperatures until decomposition. The phase diagram indicates two near isobaric phase boundaries at ~2 GPa ( I) and ~ 5 GPa ( I ) that persists from 25oC until the onset of decomposition at ~300oC. In addition, the ambient pressure, high-temperature phase transition (~111oC) lies along a steep boundary (~100oC/GPa) with an ( + + triple point at ~1 GPa and 300oC. A 0.9 GPa isobaric temperature ramping measurement indicated a limited stability range for the -phase between 0.5 – 0.9 GPa and 180 – 260oC, terminating in a ( + + triple point. With increasing pressure, the-phase exhibited a small negative dT/dP slope (up to ~0.2 GPa) before turning over to a positive 70oC/GPa slope, at higher pressures; until ~ 2 GPa, where it appears to terminate in an ( + + Phase-I) triple point. The decomposition boundary then exhibits an anomalous change of slope at an (a + Phase I + decomposition) triple point with a negative slope of ~180oC/GPa; which may indicate a structural modification to a higher symmetry than the -phase (P21/n) or evidence of a potential ‘island’ phase. The high pressure -phase has a moderate positive decomposition boundary slope of ~29oC/GPa up to 10 GPa. Additionally, the high P-T phase diagram of 2,4,6-triamino-1,3,5-trinitrobenzene (TATB) was determined from ambient pressure up to 10 GPa and decomposition. TATB appeared to remain triclinic (P1) and has a very moderate ~4oC/GPa decomposition boundary slope up to 10 GPa. The similarities between the decomposition boundaries of the -phase of FOX-7 and TATB are remarkable: both phases have triclinic symmetry and planar molecular/layering structures with moderate positive slopes extending over a broad range of pressure. These results provide the first recorded evidence of high P-T stability of two similar high explosives and the potential mechanisms behind sensitivity and performance.
Recommended Citation
Bishop, Matthew Marc, "1,1-Diamino-2,2-Dinitroethylene (Fox-7) Under High Pressure-Temperature" (2016). All ETDs from UAB. 1173.
https://digitalcommons.library.uab.edu/etd-collection/1173
