Recent Developments to Understand Molecular Changes in Shocked Energetic Materials

Gupta, Y. M.

doi:10.1051/jp4:1995427

Cited by 13 publications

(24 citation statements)

References 8 publications

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“…Despite numerous investigations to uncover the origins of sensitivity in these materials, there is not yet an understanding of how local structure in shock-compressed high explosives evolve to undergo very complex physical and chemical processes from shock initiation to a steady state detonation and why this can depend strongly on impurities and defects and even on shock direction. 1,2 Interpretations from experimental studies are complicated by heterogeneities due to surfaces, voids, and inclusions, all of which may contribute to sensitivity. The characteristics of the response to shock processes strongly depend on mechanical properties (crystal orientation, microstructure, gaps, defects, interfaces, etc.…”

Section: Introductionmentioning

confidence: 99%

Anisotropic shock sensitivity for β-octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine energetic material under compressive-shear loading from ReaxFF-lg reactive dynamics simulations

Zhou

Zybin

Liu

et al. 2012

Journal of Applied Physics

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We report here the predictions on anisotropy of shock sensitivity and of chemical process initiation in single crystal b-octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (b-HMX) using compressive shear reactive dynamics (CS-RD) model with ReaxFF-lg reactive force field. Analysis of resolved shear stress induced by uniaxial compression along three shock directions normal to (110), (011), and (010) planes leads to identify eight slip systems as candidates for shear deformation. For each of the eight slip systems, non-equilibrium reactive dynamics simulations were carried out to determine thermal, mechanical, and chemical responses to shear deformation. Shock direction normal to (010) plane exhibits large shear stress barriers arising from steric hindrance between molecules of adjacent layers leading to local dramatic energy and temperature increases under shear flow that in turn accelerate chemical bond breaking and initial product formation processes, promoting further molecular decomposition and eventually transition to detonation. This suggests that single crystal b-HMX is sensitive to shocks in direction normal to (010) plane. Shock directions normal to (110) and (011) planes reveal significantly less steric hindrance, leading to more modest energy and temperature increases followed by slower chemical reaction initiation. Thus, shock directions normal to (110) and (011) planes are less sensitive than shock direction normal to (010) plane, which agree with interpretations from currently available plate impact experiments on HMX. This validation of CS-RD and ReaxFF for characterizing sensitivity of single crystal energetic materials indicates that these methods can be applied to study sensitivity for more complex polymer bonded explosives and solid composite propellants having complex microstructures, corrugated interfaces, as well as defects. V

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Section: Introductionmentioning

confidence: 99%

Anisotropic shock sensitivity for β-octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine energetic material under compressive-shear loading from ReaxFF-lg reactive dynamics simulations

Zhou

Zybin

Liu

et al. 2012

Journal of Applied Physics

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“…1 They have the advantage of being in situ microscopic probes that complement time-resolved continuum measurements. Hence, scientific issues relevant to the development of new energetic materials, shock sensitivity, and safety of high explosives can be addressed at a fundamental level.…”

Section: Introductionmentioning

confidence: 99%

Emission and Fluorescence Spectroscopy To Examine Shock-Induced Decomposition in Nitromethane

Gruzdkov

Gupta

1998

J. Phys. Chem. A

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Time-resolved emission spectra were obtained from neat and ethylenediamine-sensitized nitromethane shocked to 12-17 GPa peak pressures using step wave loading. Broadband emission identified as chemiluminescence from nitrogen dioxide was observed due to reactions in both neat and amine-sensitized nitromethane. When laser light at 514 nm was present, fluorescence in addition to chemiluminescence was observed in shocked nitromethane-ethylenediamine mixtures; no such fluorescence was found in neat nitromethane. The fluorescing species are assigned to an intermediate formed in the first stage of decomposition in nitromethaneethylenediamine mixtures. The same intermediate was detected previously using time-resolved optical absorption spectroscopy (J. Phys. Chem. A 1998Chem. A , 102, 2322 and was inferred to be a radical anion of nitromethane, CH 3 NO 2 •-. This interpretation is consistent with the fluorescence data reported here. Laser irradiation (∼10 MW/cm 2 at 514 nm) during shock loading resulted in more intense chemiluminescence in both neat nitromethane and nitromethane-ethylenediamine mixtures. However, the effect was qualitatively different in the two cases, and the difference is attributed to different decomposition mechanisms operative initially in neat and sensitized nitromethane.

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“…Over the past several decades much work has been dedicated to elucidating the mechanisms of mechanical shock induced ignition of plastic bonded explosives (PBXs) [1][2][3][4][5][6][7][8][9][10][11][12][13]. PBXs are heterogeneous materials consisting of energetic molecular crystals embedded in a polymer matrix, which sometimes also contain taggants/markers, frictiongenerating grit, antioxidants, and plasticizers.…”

Section: Introductionmentioning

confidence: 99%

Dy3+-doped yttrium complex molecular crystals for two-color thermometry in heterogeneous materials

Anderson

Gunawidjaja

Eilers

2017

Journal of Luminescence

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We develop Dy 3+ -doped yttrium complexes for use as two-color thermometry (TCT) phosphor molecular crystals in heterogeneous materials. These complexes include: Dy:Y(acac)3(phen), Dy:Y(hfa)3(DPEPO), Dy:Y(4-BBA)3(TPPO), Dy:Y(acac)3, and Dy:Y(acac)3(DPEPO), where the Dy/Y ratio is 1:9. We characterize the materials' photoluminescence at different temperatures to determine the TCT calibration parameters and the degree to which thermal quenching influences the emission. From this data we observe a link between the excited state lifetime at room temperature and the degree to which the material is susceptible to thermal quenching (i.e. materials having long room temperature lifetimes are more resistant to thermal quenching than materials with short room temperature lifetimes). Of the five complexes tested we find that Dy:Y(acac)3(DPEPO) has the best thermal performance, with the most likely source of improvement being DPEPO's compact rigid structure. This rigidity helps with energy transfer to the Dy 3+ ion, suppresses non-radiative loss modes, and reduces exciplex formation.

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Recent Developments to Understand Molecular Changes in Shocked Energetic Materials

Cited by 13 publications

References 8 publications

Anisotropic shock sensitivity for β-octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine energetic material under compressive-shear loading from ReaxFF-lg reactive dynamics simulations

Anisotropic shock sensitivity for β-octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine energetic material under compressive-shear loading from ReaxFF-lg reactive dynamics simulations

Emission and Fluorescence Spectroscopy To Examine Shock-Induced Decomposition in Nitromethane

Dy3+-doped yttrium complex molecular crystals for two-color thermometry in heterogeneous materials

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