Ignition of Fully Dense Nanocomposite Thermite Powders by an Electric Spark

Williams, Rayon A.; Patel, Jaymin V.; Dreizin, Edward L.

doi:10.2514/1.b35073

Cited by 16 publications

(13 citation statements)

References 23 publications

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“…The ESD ignition apparatus based on model 931 firing test system by Electro-Tech Systems, Inc., was described previously (Williams et al 2012;Williams et al 2014b were qualitatively consistent between themselves for both configurations; however, specific temporal characteristic between emission traces recorded with and without fiber optics were not compared directly to each other.…”

Section: Methodsmentioning

confidence: 99%

“…It was also reported that different ignition regimes, involving individual burning particles or aerosolized powder clouds, were observed when the thickness of a metal powder layer struck by ESD varied (Williams et al 2012). Most recently, ESD ignition of reactive nanocomposite thermite powders prepared by Arrested Reactive Milling (ARM) (E.L. Dreizin and Schoenitz 2009) was studied (Shaw et al 2014;Williams et al 2014b). …”

Section: Introductionmentioning

confidence: 96%

“…100 nm; they are of interest as potential additives to solid propellants (Stamatis et al 2010), reactive structural materials (Stamatis et al 2011), and components of other energetic formulations. It was reported that two distinct spark-initiated ignition regimes were observed for nanocomposite thermites using Al as a fuel and CuO and MoO 3 as oxidizers: monolayers of composite particles ignite within 100-200 ns after the spark discharge onset producing multiple individually burning particles (Shaw et al 2014), whereas thicker powder layers ignite following a substantial (~ 0.1-5 ms) delay after the spark discharge and generate burning powder clouds (Williams et al 2014b). In addition to vastly different ignition delays, the burn times observed for individual particle and cloud combustion were very different.…”

Section: Introductionmentioning

confidence: 98%

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Electro-Static Discharge Ignition of Monolayers of Nanocomposite Thermite Powders Prepared by Arrested Reactive Milling

Monk

Williams

Liu

et al. 2015

Combustion Science and Technology

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Reactive nanocomposite powders with aluminum as a fuel and copper, bismuth, iron, and molybdenum oxide as oxidizers: 2Al·3CuO, 2.35Al·Bi 2 O 3 , 2Al·Fe 2 O 3 , and 2Al·MoO 3 , were prepared by arrested reactive milling, placed in monolayers on a conductive substrate and ignited by an electro-static discharge (ESD) or spark in air, argon, and vacuum. The ESD was produced by discharging a 2000 pF capacitor charged to a voltage varied from 5 to 20 kV. Emission from ignited particles was monitored using a photomultiplier equipped with an interference filter.Experimental variables included particle sizes, milling time used to prepare composite particles, surrounding environment, and starting ESD voltage. All materials ignited in all environments, producing individual burning particles that were ejected from the substrate. The spark duration varied from 1 to 5 µs; the duration of the produced emission pulse was in the range of 80 -250 µs for all materials studied. The longest emission duration was observed for the nanocomposite thermite using MoO 3 as an oxidizer. The reaction rates of the ESD-initiated powders were defined primarily by the scale of mixing of and reactive interface area between the fuel and oxidizer in composite materials rather than by the external particle surface or particle dimensions. In vacuum, particles were heated by ESD while remaining on the substrate until they Downloaded by [University of Nebraska, Lincoln] at 12:34 13 April 2015A c c e p t e d M a n u s c r i p t 2 began generating gas combustion products. In air and argon, particles initially pre-heated by ESD were lifted and accelerated to ca. 100 m/s by the generated shock wave; the airborne particles continued self-heating due to heterogeneous redox reactions.

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Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 96%

Section: Introductionmentioning

confidence: 98%

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Electro-Static Discharge Ignition of Monolayers of Nanocomposite Thermite Powders Prepared by Arrested Reactive Milling

Monk

Williams

Liu

et al. 2015

Combustion Science and Technology

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“…100 nm. Two distinct spark-initiated ignition regimes were observed for nanocomposite thermites using Al as a fuel and CuO and MoO 3 as oxidizers: monolayers of composite particles ignite within 100-200 ns after the spark discharge onset producing multiple individually burning particles [11], whereas thicker powder layers ignite following a substantial (~ 0.1-5 ms) delay after the spark discharge and generate burning powder clouds [10]. The burn times for clouds were in the order of several ms, comparable to the burn times of individual particles of the same thermites ignited by a CO 2 laser beam [12].…”

Section: Introductionmentioning

confidence: 97%

“…It was also reported that different ignition regimes, involving individual burning particles or aerosolized powder clouds, were observed when the thickness of a metal powder layer struck by ESD varied [6]. Most recently, ESD ignition of reactive nanocomposite thermite powders prepared by Arrested Reactive Milling (ARM) [9] was studied [10,11]. Such powders contain particles with dimensions in the range of 1 -100 µm, in which metal and oxidizer are mixed on the scale of ca.…”

Section: Introductionmentioning

confidence: 99%

Electro-static discharge ignition of monolayers of nanocomposite thermite powders prepared by Arrested Reactive Milling

et al. 2015

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Reactive nanocomposite powders with compositions 2Al•3CuO, 2.35Al•Bi 2 O 3 , 2Al•Fe 2 O 3 , and 2Al•MoO 3 were prepared by arrested reactive milling, placed in monolayers on a conductive substrate and ignited by an electro-static discharge (ESD) or spark in air, argon, and vacuum. The ESD was produced by discharging a 2000 pF capacitor charged to a voltage varied from 5 to 20 kV. Emission from ignited particles was monitored using a photomultiplier equipped with an interference filter. Experimental variables included particle sizes, milling time used to prepare composite particles, surrounding environment, and starting ESD voltage. All materials ignited in all environments, producing individual burning particles that were ejected from the substrate. The spark duration varied from 1 to 5 µs; the duration of the produced emission pulse was in the range of 80 -250 µs for all materials studied. The longest emission duration was observed for the nanocomposite thermite using MoO 3 as an oxidizer. The reaction rates of the ESD-initiated powders were defined primarily by the scale of mixing of and reactive interface area between the fuel and oxidizer in composite materials rather than by the external particle surface or particle dimensions. In vacuum, particles were heated by ESD while remaining on the substrate until they began generating gas combustion products. In air and argon, particles initially pre-heated by ESD were lifted and accelerated to ca. 100 m/s by the generated shock wave; the airborne particles continued self-heating due to heterogeneous redox reactions.

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Reactive Structural Materials: Preparation and Characterization

Hastings

Dreizin

2017

Adv Eng Mater

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Reactive structural materials, which can serve both as structural elements as well as a source of chemical energy released upon initiation have emerged as an important class of metal-based composites for use in various energetic systems. Such materials rely on a variety of exothermic reactions, from oxidation to formation of metal-metalloid and intermetallic phases. The rates of these reactions are as important as the energy that may be released, in order for them to occur at the time scales compatible with the requirements of applications. Therefore, chemical composition, scale at which reactive components are mixed, and the structure and morphology of materials are important and can be controlled by the method of preparation and compaction of the composite materials. Methods of preparation of the composite structures are briefly reviewed as well as methods of characterization of their mechanical and energetic properties. In addition to common thermo-analytical and static mechanical property measurements, dynamic tests of mechanical properties as well as ignition and combustion experiments are necessary to understand the fragmentation, initiation, and heat release expected for these materials when they are stimulated by an impact, shock, or rapid heating. Reaction mechanisms are studied presently for the thin layers and small samples of reactive materials initiated in carefully designed experiments. In other experiments, impact and explosive initiation are characterized for larger material compacts in the conditions imitating practical scenarios. Examples of results describing thermal, impact, and explosive initiation of some of the reactive materials are presented.

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Ignition of Fully Dense Nanocomposite Thermite Powders by an Electric Spark

Cited by 16 publications

References 23 publications

Electro-Static Discharge Ignition of Monolayers of Nanocomposite Thermite Powders Prepared by Arrested Reactive Milling

Electro-Static Discharge Ignition of Monolayers of Nanocomposite Thermite Powders Prepared by Arrested Reactive Milling

Electro-static discharge ignition of monolayers of nanocomposite thermite powders prepared by Arrested Reactive Milling

Reactive Structural Materials: Preparation and Characterization

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