Electro-static discharge ignition of monolayers of nanocomposite thermite powders prepared by arrested reactive milling

Ian Monk, Rayon Williams, Xinhang Liu, Edward L. Dreizin

Research output: Contribution to journalArticlepeer-review

12 Scopus citations

Abstract

Reactive nanocomposite powders with aluminum as a fuel and copper, bismuth, iron, and molybdenum oxide as oxidizers: 2Al·3CuO, 2.35Al·Bi2O3, 2Al·Fe2O3, and 2Al·MoO3, 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, which 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 MoO3 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.

Original languageEnglish (US)
Pages (from-to)1276-1294
Number of pages19
JournalCombustion Science and Technology
Volume187
Issue number8
DOIs
StatePublished - Aug 3 2015

All Science Journal Classification (ASJC) codes

  • Chemistry(all)
  • Chemical Engineering(all)
  • Fuel Technology
  • Energy Engineering and Power Technology
  • Physics and Astronomy(all)

Keywords

  • Heterogeneous reactions
  • Ignition delay
  • Reactive materials
  • Spark ignition

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