Phase diagram and decomposition of 1,1-diamino-2,2-dinitroethene single crystals at high pressures and temperatures
- Washington State Univ., Pullman, WA (United States)
The high pressure-high temperature (HP-HT) phase diagram and decomposition of FOX-7, central to understanding its stability and reactivity, were determined using optical spectroscopy and imaging measurements in hydrostatically compressed and heated single crystals. Boundaries between various FOX-7 phases (α, α’, β, γ, and ε) and melting/decomposition curves were established up to 10 GPa and 750 K. Main findings are: (i) a triple point is observed between α, β, and γ phases ~ 0.6 GPa and ~ 535 K, (ii) previously suggested δ phase is not a new phase but is partly decomposed γ phase, (iii) the α-α’ transition takes place along an isobar, whereas the α’-ε transition pressure decreases with increasing temperature, and (iv) melting/decomposition temperatures increase rapidly with pressure, with an increase in the slope at the onset of the α’-ε transition. Our results differ from the recently reported HP-HT phase diagram for nonhydrostatically compressed polycrystalline FOX-7. In addition, the observed interplay between melting and decomposition suggests the suppression of melting with pressure. Our FTIR measurements at different pressures to 3.5 GPa showed similar decomposition products, suggesting similar decomposition pathways irrespective of the pressure. Lastly, the present results provide new insights into the structural and chemical stability of an important insensitive high explosive (IHE) crystal under well-defined HP-HT conditions.
- Research Organization:
- Washington State Univ., Pullman, WA (United States). Inst. for Shock Physics
- Sponsoring Organization:
- USDOE National Nuclear Security Administration (NNSA)
- Grant/Contract Number:
- NA0002007
- OSTI ID:
- 1334532
- Journal Information:
- Journal of Physical Chemistry. C, Vol. 120, Issue 20; ISSN 1932-7447
- Publisher:
- American Chemical SocietyCopyright Statement
- Country of Publication:
- United States
- Language:
- English
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