Phase transitions and isothermal equations of state of epsilon hexanitrohexaazaisowurtzitane (CL-20)

Gump, Jared; Peiris, Suhithi M.

doi:10.1063/1.2990066

Cited by 40 publications

(40 citation statements)

References 12 publications

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“…They also noted that the c-axis showed little compression throughout the entire simulated pressure range. Expansion of one of the unit cell axes under pressure has not been evidenced in similar compression experiments on other energetic materials [11,13,14].…”

Section: Heating At Ambient Pressurementioning

confidence: 94%

Equations of state of hexanitrostilbene (HNS)

Gump

Stoltz

Mason

et al. 2012

AIP Conference Proceedings

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Abstract. Hexanitrostilbene (HNS) is an energetic ingredient that is widely used in commercial and military explosives for its thermal stability. However, characterization of its thermodynamic parameters and phase stability is lacking. Crystalline properties, such as bulk modulus and thermal expansion, are necessary to accurately predict the behavior of shocked solids using hydrodynamic codes. In order to obtain these values, equations of state of fine-particle (type IV) HNS were investigated using synchrotron angle-dispersive x-ray diffraction experiments at static high-pressure and temperature. The samples were compressed and heated using diamond anvil cells. Pressure -volume data for HNS at ambient temperature were fit to the Birch-Murnaghan and Vinet formalisms to obtain bulk modulus and its first pressure derivative. Temperature -volume data at ambient pressure were fit to obtain the volume thermal expansion coefficient.

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Section: Heating At Ambient Pressurementioning

confidence: 94%

Equations of state of hexanitrostilbene (HNS)

Gump

Stoltz

Mason

et al. 2012

AIP Conference Proceedings

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“…These results indicated that under the same loading conditions, the shock sensitivity of C-1 increases as the temperature is increased from 20 °C to 95 °C. Figure 4 also demonstrates that the initial shock pressures are almost unchanged as the specimen temperature is increased, because the coefficient of thermal expansion for the ε phase of CL-20 is relatively small [8], and the shock impedance of C-1 is almost unchanged in this temperature range. Thus, a small part of the increased sensitivity may be attributed to the increased porosity at higher temperatures, which results in more hot-spot ignition sites under shock compression.…”

Section: Figurementioning

confidence: 70%

“…The temperature of the C-1 discs rose rapidly up to about 120 °C, then slowed until about 130 °C, followed by a steady temperature rise until 142 °C. Previous studies showed that ε-CL-20 remains stable up to 120 °C, and then transforms into the γ phase at 125 °C [8,9]. Thus, the bend in the temperature profile around 125 °C indicates this phase transition.…”

Section: Preheating Experimentsmentioning

confidence: 99%

“…Another parameter that changes with temperature is the explosive density; the change in density is caused by the thermal expansion of C-1 during the heating process. The coefficient of thermal expansion for the ε phase of CL-20 is 0.00014/K in the range of 300-390 K [8]; after the ε→γ phase transition, the volume of C-1 is 6% larger [10]. The JWL EOS parameters of the reaction products were obtained by a cylinder test for the C-1 explosive.…”

Section: Numerical Simulationmentioning

confidence: 99%

“…Gump [8] found that the epsilon phase is stable under ambient pressure to a temperature of 120 °C and a phase transition to the gamma phase occurs at 125 °C. The gamma phase remains stable until thermal decomposition occurs above 150 °C.…”

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confidence: 99%

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Temperature-dependent Shock Initiation of CL-20 based High Explosives

Chen

2017

Cent. Eur. J. Energ. Mater.

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Abstract:To investigate the effects of temperature on the shock initiation characteristics of hexanitrohexaazaisowurtzitane , shock initiation experiments on heated C-1 explosive (94% epsilon phase CL-20, and 6% binder, by weight) were performed at temperatures of 20 °C, 48 °C, 75 °C, 95 °C, 125 °C, 142 °C, and 175 °C. An explosive driven flyer device was used to initiate the C-1 charges and manganin pressure gauges were embedded in the C-1 specimen to record the pressure changes with time. Our results show that C-1 becomes more sensitive as the temperature is increased from 20 °C to 95 °C. The ε to γ phase transition in CL-20 occurs at 125 °C; C-1 with CL-20 in the γ phase at 142 °C is less shock sensitive than C-1 with CL-20 in the ε phase at 95 °C or 75 °C. Compared with C-1 at 142 °C, C-1 at 175 °C shows a dramatic increase in shock sensitivity. An ignition and growth reactive flow model was used to simulate the shock initiation of C-1 at various temperatures, and the parameters were obtained by fitting the experimental data. With this parameter set, the shock initiation characteristics of C-1 for temperatures between 20 °C and 175 °C can be derived.

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Compression behavior of energetic ε‐CL‐20 crystals from density functional theory calculations

Bao

Fan

et al. 2021

J Raman Spectroscopy

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Using dispersion corrected density functional theory, we comprehensively explore the structure and the Raman spectra of hexanitrohexaazaisowurtzitane (CL‐20) crystal under hydrostatic and uniaxial compression. Through hydrostatic compression, we verify that PBE‐D2 scheme can accurately describe the crystal structure under zero pressure and high pressure. Along different orientation compressions, the CL‐20 crystal exhibits considerable anisotropy in principal stresses and shear stresses. The compression effects on the vibration properties of CL‐20 are further analyzed. Compression along the [100] orientation induces some anomalous changes for vibrational modes of the nitro groups, which are associated with changes of the spatial orientation of the nitro groups. This work is expected to shed light on the anisotropic behavior and pressure‐induced configurations transitions of CL‐20 at atomistic scale.

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Phase transitions and isothermal equations of state of epsilon hexanitrohexaazaisowurtzitane (CL-20)

Cited by 40 publications

References 12 publications

Equations of state of hexanitrostilbene (HNS)

Equations of state of hexanitrostilbene (HNS)

Temperature-dependent Shock Initiation of CL-20 based High Explosives

Compression behavior of energetic ε‐CL‐20 crystals from density functional theory calculations

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