Critical detonation thickness in vapor-deposited pentaerythritol tetranitrate (PETN) films

Tappan, Alexander S.; Knepper, Robert; Wixom, Ryan R.; Marquez, Michael P.; Ball, J. Patrick; Miller, Jill C.

doi:10.1063/1.3686369

Cited by 19 publications

(13 citation statements)

References 3 publications

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“…In the past several years, multiple research groups have developed tabletop shock generation systems to facilitate a greater understanding of the many facets of the complex phenomena involved in topics ranging from detonation propagation [6,7], to chemical reaction pathways under shock conditions [8][9][10][11], and hot spot temperature measurements [12,13]. With the exception of the work of Tappan et al on microenergetics, where research is conducted at the limit of failing detonation to gain insight into these fail-ure mechanisms [7,14], the sample dimensions in these experiments are below the dimension where traditional detonations can occur [15,16] because the diameter is below the critical diameter and the run distance is often less than the length of the reaction zone.…”

Section: Introductionmentioning

confidence: 99%

Shock Initiation Microscopy with High Time and Space Resolution

Bassett

Johnson

Salvati

et al. 2020

Propellants Explo Pyrotec

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We describe studies of shock initiation and shock‐to‐detonation transitions in energetic materials using a tabletop shock compression microscope with nanosecond time resolution and micrometer spatial resolution. Planar input shocks with durations of 4–20 ns are produced using 0–4.5 km/s laser‐launched flyer plates. Emphasis is on measurements of temperature, velocities, pressure, and microstructure using photon Doppler velocimetry (PDV), optical pyrometry and high‐speed videography. Techniques are discussed for fabricating disposable shock target arrays of tiny plastic‐bonded explosives (PBX), liquid and powder explosives, and single‐crystal explosives for high‐throughput studies. Optical temperature measurements of shocked triaminotrinitrobenzene (TATB) are discussed. Since TATB is yellow, we developed methods to correct for the blue absorption to obtain more accurate temperatures. Hot spots in shocked polymer‐encased HMX (octahydro‐1,3,5,7‐tetranitro‐1,3,5,7‐tetrazocine) crystals are observed in real‐time, showing a hot spot produced in a collapsing void that ignites a deflagration. Despite the small dimensions of our explosive charges (typically 1 mm diameter and 250 μm length), we produced reproducible detonation states in solid and liquid explosives using short‐duration shocks near the von Neumann spike (VNS) pressure. We show the VNS pressure is associated with a transition to high‐efficiency gas production from the explosives. In studies of NM, prior to detonation, we see reaction originating at hot spots which coalesce to form a superdetonation.

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Section: Introductionmentioning

confidence: 99%

Shock Initiation Microscopy with High Time and Space Resolution

Bassett

Johnson

Salvati

et al. 2020

Propellants Explo Pyrotec

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“…We are pursuing external collaborations with experts on the production of well-characterized physicalvapor-deposited energetic materials samples. [18] We will revisit the Buelow sample configuration. First, to make free surface velocity measurements on the SS target foil --to better estimate the shock inputs to the energetic materials.…”

Section: Future Directionsmentioning

confidence: 99%

Benchtop energetics progress

Fajardo¹,

Fossum²,

Molek³

et al. 2012

AIP Conference Proceedings

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Abstract.We have constructed an apparatus for investigating the reactive chemical dynamics of mgscale energetic materials samples. We seek to advance the understanding of the reaction kinetics of energetic materials, and of the chemical influences on energetic materials sensitivity. We employ direct laser irradiation, and indirect laser-driven shock, techniques to initiate thin-film explosive samples contained in a high-vacuum chamber. Expansion of the reacting flow into vacuum quenches the chemistry and preserves reaction intermediates for interrogation via time-of-flight mass spectrometry (TOFMS). By rastering the sample coupon through the fixed laser beam focus, we generate hundreds of repetitive energetic events in a few minutes. A detonation wave passing through an organic explosive, such as pentaerythritol tetranitrate (PETN, C 5 H 8 N 4 O 12 ), is remarkably efficient in converting the solid explosive into final thermodynamically-stable gaseous products (e.g. N 2 , CO, CO 2 , H 2 O…). Termination of a detonation at an explosive-to-vacuum interface produces an expanding pulse of hyperthermal molecular species, with leading-edge velocities ~ 10 km/s. In contrast, deflagration (subsonic combustion) of PETN in vacuum produces mostly reaction intermediates, such as NO and NO 2 , with much slower molecular velocities; consistent with expansion-quenched thermal decomposition of PETN. We propose to exploit these differences in product chemical identities and molecular species velocities to provide a chemically-based diagnostic for distinguishing between "detonation-like" and deflagration events. We report recent progress towards the quantitative detection of hyperthermal neutral species produced by direct laser ablation of aluminum metal and of organic energetic materials, as a step towards demonstrating the ability to discriminate slow reaction intermediates from fast thermodynamically-stable final products.

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“…[5][6][7][8] The experiment uses a PETN structure to detonate the two HNAB lines simultaneously. Passive optical fiber probes are held orthogonally to each HNAB line with a polycarbonate lid.…”

Section: Figurementioning

confidence: 99%

“…The exception is the first presentation of Sandia's critical detonation thickness experiment, in which we performed an early investigation of detonation failure as a function of both film thickness and width in pentaerythritol tetranitrate (PETN). [5] Later work investigated detonation failure in PETN with microstructural changes arising from different deposition conditions, [6] and confinement effects on detonation failure in hexanitroazobenzene (HNAB), both in what we believe to be an infinite slab geometry. [7] This paper presents a preliminary investigation into the effects of geometry on HNAB detonation failure when the width is below the value where it can be considered effectively infinite.…”

Section: Introductionmentioning

confidence: 99%

Geometry effects on detonation in vapor-deposited hexanitroazobenzene (HNAB)

Tappan¹,

Wixom²,

Knepper³

2017

AIP Conference Proceedings

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Abstract. Physical vapor deposition is a technique that can be used to produce explosive films with controlled geometry and microstructure. Films of the high explosive hexanitroazobenzene (HNAB) were deposited by vacuum thermal evaporation. HNAB deposits in an amorphous state that crystallizes over time into a polycrystalline material with high density and a consistent porosity distribution. In previous work, we evaluated detonation critical thickness in HNAB films in an effectively infinite slab geometry with insignificant side losses. In this work, the effect of geometry on detonation failure was investigated by performing experiments on films with different thicknesses, while also changing lateral dimensions such that side losses became significant. The experimental failure thickness was determined to be 75.5 μm and 71.6 μm, for 400 μm and 1600 μm wide HNAB lines, respectively. It follows from this that the minimum width to achieve detonation behavior representing an infinite slab configuration is greater than 400 μm.

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Critical detonation thickness in vapor-deposited pentaerythritol tetranitrate (PETN) films

Cited by 19 publications

References 3 publications

Shock Initiation Microscopy with High Time and Space Resolution

Shock Initiation Microscopy with High Time and Space Resolution

Benchtop energetics progress

Geometry effects on detonation in vapor-deposited hexanitroazobenzene (HNAB)

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