Observing Hot Spot Formation in Individual Explosive Crystals Under Shock Compression

Johnson, Belinda P.; Zhou, Xuan; Ihara, Hoya; Dlott, Dana D.

doi:10.1021/acs.jpca.0c02788

Cited by 46 publications

(33 citation statements)

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“…The mechanism of reducing sensitivity is illustrated in Figure 10. The formation of hotspots is the main reason inducing the explosion of explosives 41 and is formed after undergoing some extrinsic stimulations and three processes: generation, growth, and spreading. The recrystallization process under the condition of freeze-drying technology can not only reduce impurities and cracks but also improve the crystal morphology; moreover, the particle size of the explosives is decreased and the uniform distribution improved significantly.…”

Section: Composition and Structure Analysismentioning

confidence: 99%

Nitrated Bacterial Cellulose-Based Energetic Nanocomposites as Propellants and Explosives for Military Applications

Ling

Cao²,

Gao³

et al. 2021

ACS Appl. Nano Mater.

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In this study, nitrated bacterial cellulose (NBC) energetic binder was introduced to prepare NBC-based nanocomposite energetic materials (nEMs) through a combined simple and safe sol−gel method and the freeze-drying technology. A series of analytical and test methods were systematically conducted to characterize the structure, composition, thermal properties, and safety performance of the materials. The results indicated that the particles of nitramine explosives were dispersed and embedded homogeneously in the three-dimensional (3D) porous cross-linked construction of the NBC gel matrix; the crystal growth of the explosive particles was restricted, which led to nanometer-scale composites. The thermal analysis demonstrated that the peak temperature of the composite (e.g., NBC/CL-20: 224.8 °C) was reduced and produced substantial heat release (e.g., NBC/CL-20: 3346 J•g −1 ) during the process of decomposition. In addition, the mechanism of thermal decomposition was probed, and cyclic catalytic decomposition between the NBC gel and explosives may exist. The sensitivity decreased visibly because of the existence of the cross-linked structure of the gel matrix, which could act as a buffer system to mitigate the release stimulated from the surroundings. Accordingly, this investigation may provide the promising potential for NBCbased energetic composites used in explosives and propellants in the military, and further promote the methodology for manufacturing energetic nanocomposites.

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Section: Composition and Structure Analysismentioning

confidence: 99%

Nitrated Bacterial Cellulose-Based Energetic Nanocomposites as Propellants and Explosives for Military Applications

Ling

Cao²,

Gao³

et al. 2021

ACS Appl. Nano Mater.

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“…We use a model system that can be described as a deconstructed PBX: a single crystal of a high explosive embedded in a transparent polyurethane (PU) matrix. 17 With this geometry, we can see through the polymer to observe hot spots produced on the single crystal, as opposed to actual PBX which are generally opaque. The single crystals used here were HMX [cyclotetramethylene-tetranitramine, (CH 2 −N−NO extremely powerful high explosive with a detonation velocity of 9 km/s and a detonation pressure of 40 GPa.…”

Section: ■ Introductionmentioning

confidence: 99%

“…With HMX-SC, hot spots are produced at the HMX−polymer interface, typically at crystal corners or edges. 17 The hot spots and deflagrations are probed by simultaneous high-speed multiframe imaging and optical pyrometry. 17 Our high-speed camera provides four images on a single shot with 20 ns acquisition time and a high spatial resolution of 2 μm.…”

Section: ■ Introductionmentioning

confidence: 99%

“…17 The hot spots and deflagrations are probed by simultaneous high-speed multiframe imaging and optical pyrometry. 17 Our high-speed camera provides four images on a single shot with 20 ns acquisition time and a high spatial resolution of 2 μm. The incomplete picture provided by just four images per shot with nominal time resolution is greatly enhanced by the pyrometer, which provides a continuous stream of spatially averaged temperatures and emissivities with 2 ns time resolution.…”

Section: ■ Introductionmentioning

confidence: 99%

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Shock Pressure Dependence of Hot Spots in a Model Plastic-Bonded Explosive

2022

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Shock initiation of plastic-bonded explosives (PBX) begins with the formation of so-called “hot spots”, which are energetic reactions localized in regions where the PBX microstructure concentrates the input shock wave energy. We developed a model PBX system to study hot spots which consists of a single crystal of the high explosive HMX (cyclotetramethylene-tetranitramine) embedded in a transparent polyurethane binder (J. Phys Chem. A, 2020, 124, 4646–4653). In the current work we use this model system to study the influence of input shock pressure (12–26 GPa) on hot spot generation using micrometer-resolved high-speed imaging and nanosecond-resolved optical pyrometry. By shocking ∼100 HMX single crystals (HMX-SC), two distinct shock pressure thresholds were observed. The threshold for producing single hot spots in some crystals was 15 GPa. At 23 GPa, hot spot density was sufficiently high to lead to rapid deflagration of the entire HMX-SC. It takes about 25 ns after the shock passes for the hot spots to appear to our visible-light detection apparatus which has a noise floor at about 2000 K. That indicates the shock produces nascent hot spots that undergo a thermal explosion that reaches temperatures >2000 K in 25 ns. The initial hot spot temperature is roughly 3800 K which settles down to 3400 K, the adiabatic flame temperature of HMX. The higher initial temperature is attributed to release of stored interfacial strain energy produced by the shock. An initial estimate for the velocity of the flame front originating at an HMX hot spot is 550 m/s.

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“…Alongside the synthesis of novel compounds with enhanced performance and safety, [1][2][3][4] current trends in energetic materials (EM) research include fundamental studies into the combustion, initiation, and detonation phenomena. [5][6][7][8][9] The initiation of an explosion is a particularly complex phenomenon involving chemical decomposition, phase transitions, and mechanical transformations. [10][11][12][13] The recent ability to observe initiation with significantly enhanced spatial and temporal resolution promises new insights into the mechanism of this process.…”

Section: Introductionmentioning

confidence: 99%