Control of Crystal Density of ε-Hexanitrohexaazaisowurzitane in Evaporation Crystallization

Lee, Myungho; Kim, Jun-Hyung; Park, Young-Chul; Hwang, Ji-Hwan; Kim, Woo‐Sik

doi:10.1021/ie0608152

Cited by 22 publications

(11 citation statements)

References 14 publications

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“…This result is consistent with the statically calculated results of low transition barriers. Hence, this coexistence should be a basis for the easy polymorphic transitions of CL-20 in solvents observed experimentally. − …”

Section: Resultsmentioning

confidence: 92%

“…The ε-form presents the highest packing density of approximately 2.04 g/cm 3 and the best stability against thermal and impact stimuli. Thus, the crystal engineering of CL-20s mainly aims to achieve an ε-formed polymorph, avoiding transformation to other less stable ones. − Crystallization conditions, such as solvents, addition method, temperature, and agitation rate, can distinctively affect the polymorphs of CL-20 and their transformations. For example, polymorphs of CL-20 transform more easily in solutions than in solids.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Comparative Study of Experiments and Calculations on the Polymorphisms of 2,4,6,8,10,12-Hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane (CL-20) Precipitated by Solvent/Antisolvent Method

Wei

et al. 2016

J. Phys. Chem. C

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2,4,6,8,10,12-Hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane (CL-20) is the most powerful explosive. However, the application of this compound is limited by its high sensitivity and serious polymorphic transformations. Thus, elucidating the mechanism of crystallization and polymorphic transformation of CL-20 is crucial. This work presents a comparative study of experiments and calculations to clarify the mechanism of CL-20 precipitation using an solvent/antisolvent method. Calculations show that the β-formed CL-20 conformations are always the most energetically favored. These conformations have generally the highest content in solutions, and the intermolecular conformational transformations in solutions have low energy barriers. In addition, it is predicted that the β-CL-20 crystal possesses the lowest lattice energy among all polymorphs. The calculated results are successfully applied to explain the experimental observations, as β-CL-20 crystal is initially precipitated from most of the highly supersaturated solutions and then converted into ε-CL-20 crystal. This precipitation is kinetically controlled by the dominance of β-CL-20 molecules in a metastable phase and rapid crystallization. The final conversion into ε-CL-20 crystal is attributed to its low energy barrier for polymorphic transformation and stability, that is, the conversion is dynamically dominated. Furthermore, calculated coherent energy densities (CEDs) of various CL-20 polymorphs, including hydrates with different hydration degrees, agree well with the thermal stabilities, as the higher CED corresponds to the higher thermal stability. Therefore, the complex crystallization of CL-20 is elucidated by combining experimental observations with theoretical calculations and simulations.

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Section: Resultsmentioning

confidence: 92%

Section: Introductionmentioning

confidence: 99%

Comparative Study of Experiments and Calculations on the Polymorphisms of 2,4,6,8,10,12-Hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane (CL-20) Precipitated by Solvent/Antisolvent Method

Wei

et al. 2016

J. Phys. Chem. C

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“…Additionally, ultrasound effect can also diminish the size to nanoscale. [21] reports. The nano-CL-20 samples exhibit different XRD patterns, and it was found that the patterns exhibit a strong diffraction peak at 13.6 ∘ , 28.2 ∘ , and 24.1 ∘ , which corresponded to the (111), (212), and (132) crystal faces 2 of phase form (JCPDS 52-2432), demonstrating that the obtained crystal structure of nano-CL-20 was phase [22].…”

Section: Resultsmentioning

confidence: 99%

Preparation of CL-20 Explosive Nanoparticles and Their Thermal Decomposition Property

Wang

Gao

Yang

et al. 2016

Journal of Nanomaterials

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Herein, we develop a novel method for preparing nanohexanitrohexaazaisowurtzitane (nano-CL-20) via ultrasonic spray-assisted electrostatic adsorption (USEA) technology. Various experimental conditions which influence safety factors and the crystallization process were studied. Meanwhile, the prepared nano-CL-20 particles were characterized by field emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), and Fourier transform infrared (FT-IR) spectroscopy. The results show that the obtained nano-CL-20 showed a wide size distribution in the range from 150 to 600 nm with an average of 270 nm. Moreover, their thermal properties were also investigated by differential scanning calorimetry (DSC) and thermogravimetry (TG). For nano-CL-20, the exothermal peak is 232.9°C increased by 12°C compared with conventionally manufactured (CM) CL-20, and they exhibit fast energy release efficiency as well as more energy release. The simple and continuous approach presented here is expected to be an attractive potential for fabricating other organic nanoparticles.

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“…Four of the polymorphs (α, β, γ, and ε) exist at ambient pressure and temperature. Only ε-HNIW is applied in practice because of its good thermal stability and the highest energy density [15][16][17][18] (theoretical density of 2.044 g·cm −3 [19]). However, the ε-phase can be converted to other phases under extreme conditions [20].…”

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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Control of Crystal Density of ε-Hexanitrohexaazaisowurzitane in Evaporation Crystallization

Cited by 22 publications

References 14 publications

Comparative Study of Experiments and Calculations on the Polymorphisms of 2,4,6,8,10,12-Hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane (CL-20) Precipitated by Solvent/Antisolvent Method

Comparative Study of Experiments and Calculations on the Polymorphisms of 2,4,6,8,10,12-Hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane (CL-20) Precipitated by Solvent/Antisolvent Method

Preparation of CL-20 Explosive Nanoparticles and Their Thermal Decomposition Property

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

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