Putting the squeeze on energetic materials—structural characterisation of a high-pressure phase of CL-20

Millar, David I. A.; Maynard-Casely, Helen E.; Kleppe, Annette K.; Marshall, William G.; Pulham, Colin R.; Cumming, Adam S.

doi:10.1039/c002701d

Cited by 64 publications

(61 citation statements)

References 17 publications

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“…Five conformational polymorphs and an hydrate form have been found so far [18][19][20][21], but only four directly produced in many HNIW synthesis techniques and need recrystallization [22][23][24][25]. However, there often exists other polymorphs in form e from recrystallization, which will decrease the density, enhance the sensitivity and then reduce the performance of HNIW.…”

Section: Introductionmentioning

confidence: 99%

Polymorphism in hexanitrohexaazaisowurtzitane crystallized from solution

Tian

Liu

et al. 2012

Journal of Crystal Growth

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Section: Introductionmentioning

confidence: 99%

Polymorphism in hexanitrohexaazaisowurtzitane crystallized from solution

Tian

Liu

et al. 2012

Journal of Crystal Growth

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“…Therefore, it is necessary and meaningful to explore the pressure behaviors for energetic materials. Except for studying the phase transitions and decomposition mechanism of CL‐20 under pressure, early study has made a clear knowledge about the structural characterization of a high‐pressure phase of CL‐20 through experiments . Gump et al investigated the structural changes of ϵ‐CL‐20 under high pressure, showing that the unit cell volume decreased under compression and no phase was observed up to 6.3 GPa .…”

Section: Introductionmentioning

confidence: 99%

Structures, Elasticity, and Sensitivity Characteristics of ɛ‐CL‐20 under High Pressure from First‐Principles Calculations

Zhong

Qin

Liu

et al. 2019

Physica Status Solidi (b)

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First‐principles calculations have been conducted for ɛ‐CL‐20 to study the pressure effects on the structures, elasticity, and sensitivity characteristics under 0–75 GPa. It is found that N–NO2 possesses smaller populations than other bonds and is verified as the trigger bond for ϵ‐CL‐20, and the nitrogen atoms on nitro groups (–NO2) are more sensitive to pressure than that on the rings. A detailed understanding of elasticity has been studied and discussed under pressure. In general, the mechanical properties of ɛ‐CL‐20 are distinctly enhanced under compression. The obtained elastic constants show better agreement with the experiment at zero pressure. As the pressure increases, the lattice interactions towards different directions present pronounced difference. A relationship of C11 ≈ C33 > C22 is obtained in the lower pressure region. However, a different relationship of C11 > C22 ≈ C33 is predicted under higher pressure. The crystal, ɛ‐CL‐20, changes from brittleness to plasticity according to the sharp increase of B/G and C12–C44 under compression. And the band gap of ɛ‐CL‐20 decreases with the increasing pressure, indicating the crystal becomes more sensitive under compression.

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“…The different extended orientations of the nitro groups relative to the five-or six-membered rings of HNIW leads to different molecular packing models and different numbers of molecules in a cell, which defines several probable polymorphs of HNIW. So far, five different polymorphs (α, β, γ, ε, and ζ) have been reported and identified [10][11][12][13][14]. Four of the polymorphs (α, β, γ, and ε) exist at ambient pressure and temperature.…”

Section: Introductionmentioning

confidence: 99%

Thermally Induced Polymorphic Transformation of Hexanitrohexaazaisowurtzitane (HNIW) Investigated by in-situ X-ray Powder Diffraction

Liu¹,

Li²,

Ze-shan³

et al. 2016

Cent. Eur. J. Energ. Mater.

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Abstract:The ε→γ phase transition of HNIW induced by heat was investigated with in situ X-ray powder diffraction (PXRD). The effects of purity, particle size, insensitive additives and the time of isothermal heat treatment on the phase transition were evaluated. It was found that the phase transition is irreversible with changes in temperature, and the two phases can coexist in a certain temperature range. Moreover, the initial phase transition temperature increases with increasing purity and decreasing particle size of HNIW, and thus with the approximate crystal density. The addition of graphite and paraffin wax to HNIW as insensitive additives leads to a decrease in the initial phase transition temperature, but the addition of TATB does not affect the initial phase transition temperature. Thus, TATB is a suitable insensitive additive. Moreover, at the critical temperature, the isothermal time determined the efficiency of the ε-to γ-phase transition. This work lays the foundations for the choice of molding technologies, performance test methods, ammunition storage options, as well as the manufacture of HNIWbased explosive formulations.

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Putting the squeeze on energetic materials—structural characterisation of a high-pressure phase of CL-20

Cited by 64 publications

References 17 publications

Polymorphism in hexanitrohexaazaisowurtzitane crystallized from solution

Polymorphism in hexanitrohexaazaisowurtzitane crystallized from solution

Structures, Elasticity, and Sensitivity Characteristics of ɛ‐CL‐20 under High Pressure from First‐Principles Calculations

Thermally Induced Polymorphic Transformation of Hexanitrohexaazaisowurtzitane (HNIW) Investigated by in-situ X-ray Powder Diffraction

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