Phase Retransformation and Void Evolution of Previously Heated HMX-Based Plastic-Bonded Explosive in Wet Air

Yan, Guanyun; Zhao, Fan; Huang, Shiliang; Liu, Jiahui; Wang, Yunlong; Tian, Qiang; Bai, Liangfei; Gong, Jian; Sun, Guangai; Wang, Xiaolin

doi:10.1021/acs.jpcc.7b04165

Cited by 27 publications

(15 citation statements)

References 37 publications

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“…Apart from chemical components, crystal properties, including phase structures, grain sizes, and surface and internal defects, are known to have a significant influence on the mechanical strength, sensitivity, and stability of high explosives. − HMX (octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine) is an eight-membered heterocyclic high-energy explosive that has been widely used for military weapons, aerospace applications, and modern industrial applications − because of its characteristics of high energy density, good thermal stability, high detonation performance, and product cleanliness. By controlling the crystallization rate in the solution, we can observe four crystal structures, including three pure crystallization phases of α, β, and γ and a hydrate γ structure, at ambient conditions. − The β phase is the most thermodynamically stable polymorph that has the highest density and is the only one used in weapons.…”

Section: Introductionmentioning

confidence: 99%

Phase Confirmation and Equation of State of β-HMX under 40 GPa

et al. 2019

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Phase transitions of the β-HMX crystal have been systematically studied via Raman, mid-infrared, and X-ray diffraction techniques under high pressures of up to 40 GPa. When using a neon pressure transmitting medium, we observed four phase transitions, including β-phase to ζ-phase at 5.4 GPa, ε-phase at 9.6 GPa, φ-phase at 21.6 GPa, and further to η-phase at 35.0 GPa. According to the high-pressure Raman spectra, the first two phase transitions of HMX are induced by the changes of the NO 2 groups and ring, whereas the ε to φ phase transition is attributed to the mutation of the CH 2 groups and ring. Under higher pressures, another newly discovered phase transition from φ to η occurred at 35.0 GPa. Based on the analysis of highpressure X-ray diffraction results, all currently observed high-pressure phases are isostructures of monoclinic HMX, and no abrupt change in the volume has been found in the volume−pressure curve below 38 GPa. These are consistent with the isentropic compression results and the conclusion of the first-principles calculation. The present work clarifies the controversial pressure-induced phase transitions for β-HMX and the newly discovered phase transitions under high pressure.

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Section: Introductionmentioning

confidence: 99%

Phase Confirmation and Equation of State of β-HMX under 40 GPa

et al. 2019

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“…Solid–solid polymorphic transitions ubiquitously exist in organic and inorganic crystals related to photoelectric materials, , pharmaceuticals, and energetic materials . Since the properties of materials could be significantly changed accompanied by the polymorphic transition, understanding how the phase transforms and how to stabilize the phase form are fundamental questions in the research field correlated with polymorphic crystals. , Various reports have demonstrated that the polymorphic transition can be tuned through substitution of some ions or doping with other particular ions. − However, this strategy is not suitable for organic molecular crystals.…”

Section: Introductionmentioning

confidence: 99%

Kinetics for Inhibited Polymorphic Transition of HMX Crystal after Strong Surface Confinement

et al. 2019

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The kinetics and the tuning mechanisms for the polymorphic transitions remain poorly understood. In this work, the mechanisms for the inhibited β → δ polymorphic transition of 1,3,5,7-tetranitro-1,3,5,7-tetrazocane (HMX) crystal after strong surface confinement in poly(dopamine) (PDA) were studied thoroughly by nonisothermal and isothermal kinetics. The activation energy for the polymorphic transition of HMX was about 400 kJ mol–1, which was almost independent of the conversion extent. The transition process followed the three-dimensional growth of nuclei (A3) model. As for HMX@PDA, the activation energies increased from 100 to 620 kJ mol–1 with increasing conversion from 0 to 1.0. The transition process could be divided into two partially overlapped stages, i.e., the first transition step follows some mechanism between the first-order reaction model and the two-dimensional diffusion (D2) model and the second step of HMX@PDA approaches the two-dimensional nucleation and nucleus growth (A2) model. It has been demonstrated that nucleation was the rate-limiting step during the polymorphic transition. The PDA coating significantly decreased the polymorphic transition rate, especially for the nucleation process. In particular, it was decreased by 108 times compared to the uncoated HMX. Based on the density functional theory calculation and systematic characterizations, the inhibition of this transition was attributed to the strong interactions between the polymer chain of PDA and the function groups on the surface of HMX crystal, which blocked the formation of δ-nuclei at the crystal surface.

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“…The phase before and after heating was identified by neutron diffraction. Because water can accelerate the δ- to β-HMX retransformation, two parallel experiments were designed to evaluate if any different processes exist in dry and humid circumstance. HMX-d8 (2.5 g; hereafter named sample 1#) was directly put into a sealed ϕ 10 mm × 20 mm capsule made by Ti/Zr alloy after being cooled down to room temperature (RT) in a dry furnace.…”

Section: Experiments and Methodsmentioning

confidence: 99%

Acceleration of δ- to β-HMX-D8 Phase Retransformation with D₂O and Intergranular Strain Evolution in a HMX-Based Polymer-Bonded Explosive

Liu

Bai

et al. 2019

J. Phys. Chem. C

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3,5,3,5, is one of the most widely used explosives. Problems about phase state and unrecoverable damage are significant in the application of HMX and HMX-based polymer-bonded explosive (PBX). Recently, the acceleration of δto β-HMX retransformation in humid atmosphere was reported. However, the function of water was not well understood. In this paper, we studied the mixed phase during δto β-HMX-d8 retransformation with neutron diffraction. Evidence of γ-HMX-d8 is specially focused to estimate whether the hydrated phase is part of the δto βphase retransformation. Besides, in situ high-pressure neutron diffraction of HMX-based PBX was performed to study the evolution of intergranular strains in special structures such as twin plane, cleavage planes, and slip systems. We observed an abnormal release of strain on certain planes under applied pressure which had not been reported. This abnormal phenomenon was considered to explain the formation of microcracks in HMX.

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Phase Retransformation and Void Evolution of Previously Heated HMX-Based Plastic-Bonded Explosive in Wet Air

Cited by 27 publications

References 37 publications

Phase Confirmation and Equation of State of β-HMX under 40 GPa

Phase Confirmation and Equation of State of β-HMX under 40 GPa

Kinetics for Inhibited Polymorphic Transition of HMX Crystal after Strong Surface Confinement

Acceleration of δ- to β-HMX-D8 Phase Retransformation with D₂O and Intergranular Strain Evolution in a HMX-Based Polymer-Bonded Explosive

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Phase Retransformation and Void Evolution of Previously Heated HMX-Based Plastic-Bonded Explosive in Wet Air

Cited by 27 publications

References 37 publications

Phase Confirmation and Equation of State of β-HMX under 40 GPa

Phase Confirmation and Equation of State of β-HMX under 40 GPa

Kinetics for Inhibited Polymorphic Transition of HMX Crystal after Strong Surface Confinement

Acceleration of δ- to β-HMX-D8 Phase Retransformation with D2O and Intergranular Strain Evolution in a HMX-Based Polymer-Bonded Explosive

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Acceleration of δ- to β-HMX-D8 Phase Retransformation with D₂O and Intergranular Strain Evolution in a HMX-Based Polymer-Bonded Explosive