Phase stability of {epsilon} and {gamma} HNIW (CL-20) at high-pressure and temperature

Hexanitrohexaazaisowurtzitane (CL-20) is one of the few ingredients developed since World War II to be considered for transition to military use. Five polymorphs have been identified for CL-20 by FTIR measurements ({alpha}, {beta}, {gamma}, {epsilon}, {zeta}). As CL-20 is transitioned into munitions...

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Bibliographic Details
Published in:AIP conference proceedings 2007-12, Vol.955 (1)
Main Authors: Gump, Jared C., Stoltz, Chad A., Peiris, Suhithi M.
Format: Article
Language:English
Subjects:
AMBIENT TEMPERATURE
COMPRESSION
COMPUTERIZED SIMULATION
DIAMONDS
EQUATIONS OF STATE
EVALUATION
FOURIER TRANSFORMATION
INFRARED SPECTRA
MATERIALS SCIENCE
ORGANIC COMPOUNDS
PHASE DIAGRAMS
PHASE STABILITY
PHASE TRANSFORMATIONS
PRESSURE RANGE GIGA PA
PYROLYSIS
THERMODYNAMIC PROPERTIES
X-RAY DIFFRACTION
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Summary:Hexanitrohexaazaisowurtzitane (CL-20) is one of the few ingredients developed since World War II to be considered for transition to military use. Five polymorphs have been identified for CL-20 by FTIR measurements ({alpha}, {beta}, {gamma}, {epsilon}, {zeta}). As CL-20 is transitioned into munitions it will become necessary to predict its response under conditions of detonation, for performance evaluation. Such predictive modeling requires a phase diagram and basic thermodynamic properties of the various phases at high pressure and temperature. Therefore, the epsilon and gamma phases of CL-20 at static high-pressure and temperature were investigated using synchrotron angle-dispersive x-ray diffraction experiments. The samples were compressed and heated using diamond anvil cells (DAC). Pressures and temperatures achieved were around 5 GPa and 240 deg. C, respectively. The epsilon phase was stable to 6.3 GPa at ambient temperature. When heated at ambient pressure the epsilon phase was sustained to a temperature of 120 deg. C then underwent a transition to the gamma phase above 125 deg. C and then thermal decomposition occurred above 150 deg. C. Upon compression, the gamma phase underwent a phase transition at both ambient temperature and 140 deg. C. Pressure--volume data for the epsilon and gamma phase at ambient temperature and the epsilon phase at 75 deg. C were fit to the Birch-Murnaghan formalism to obtain isothermal equations of state.
ISSN:0094-243X
1551-7616
DOI:10.1063/1.2832955