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Title: Shock initiation of nano-Al/Teflon: High dynamic range pyrometry measurements

Abstract

In this paper, laser-launched flyer plates (25 μm thick Cu) were used to impact-initiate reactive materials consisting of 40 nm Al particles embedded in Teflon AF polymer (Al/Teflon) on sapphire substrates at a stoichiometric concentration (2.3:1 Teflon:Al), as well as one-half and one-fourth that concentration. A high dynamic range emission spectrometer was used to time and spectrally resolve the emitted light and to determine graybody temperature histories with nanosecond time resolution. At 0.5 km s -1, first light emission was observed from Teflon, but at 0.6 km s -1, the emission from Al/Teflon became much more intense, so we assigned the impact threshold for Al/Teflon reactions to be 0.6 (±0.1) km s -1. The flyer plates produced a 7 ns duration steady shock drive. Emission from shocked Al/Teflon above threshold consisted of two bursts. At the higher impact velocities, the first burst started 15 ns after impact, peaked at 25 ns, and persisted for 75 ns. The second burst started at a few hundred nanoseconds and lasted until 2 μs. The 15 ns start time was exactly the time the flyer plate velocity dropped to zero after impact with sapphire. The first burst was associated with shock-triggered reactions and themore » second, occurring at ambient pressure, was associated with combustion of leftover material that did not react during shock. The emission spectrum was found to be a good fit to a graybody at all times, allowing temperature histories to be extracted. At 25 ns, the temperature at 0.7 km s -1 and the one-fourth Al load was 3800 K. Those temperatures increased significantly with impact velocity, up to 4600 K, but did not increase as much with Al load. A steady combustion process at 2800 (±100) K was observed in the microsecond range. Finally, the minimal dependence on Al loading indicates that these peak temperatures arise primarily from Al nanoparticles reacting almost independently, since the presence of nearby heat sources had little influence on the peak temperatures.« less

Authors:
ORCiD logo [1];  [1]; ORCiD logo [1]
  1. Univ. of Illinois, Urbana, IL (United States). School of Chemical Sciences
Publication Date:
Research Org.:
Univ. of Illinois at Urbana-Champaign, IL (United States)
Sponsoring Org.:
USDOE National Nuclear Security Administration (NNSA); US Army Research Office (ARO); Defense Threat Reduction Agency (DTRA) (United States)
OSTI Identifier:
1465329
Grant/Contract Number:  
NA0002006; W911NF-13-1-0217; HDTRA1-12-1-0011
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Journal of Applied Physics
Additional Journal Information:
Journal Volume: 121; Journal Issue: 8; Journal ID: ISSN 0021-8979
Publisher:
American Institute of Physics (AIP)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; nanoparticles; decomposition reactions; shock wave effects; aluminium; laser impact; cameras; emission spectra; combustion; sapphire

Citation Formats

Wang, Jue, Bassett, Will P., and Dlott, Dana D.. Shock initiation of nano-Al/Teflon: High dynamic range pyrometry measurements. United States: N. p., 2017. Web. doi:10.1063/1.4977109.
Wang, Jue, Bassett, Will P., & Dlott, Dana D.. Shock initiation of nano-Al/Teflon: High dynamic range pyrometry measurements. United States. doi:10.1063/1.4977109.
Wang, Jue, Bassett, Will P., and Dlott, Dana D.. Tue . "Shock initiation of nano-Al/Teflon: High dynamic range pyrometry measurements". United States. doi:10.1063/1.4977109. https://www.osti.gov/servlets/purl/1465329.
@article{osti_1465329,
title = {Shock initiation of nano-Al/Teflon: High dynamic range pyrometry measurements},
author = {Wang, Jue and Bassett, Will P. and Dlott, Dana D.},
abstractNote = {In this paper, laser-launched flyer plates (25 μm thick Cu) were used to impact-initiate reactive materials consisting of 40 nm Al particles embedded in TeflonAF polymer (Al/Teflon) on sapphire substrates at a stoichiometric concentration (2.3:1 Teflon:Al), as well as one-half and one-fourth that concentration. A high dynamic range emission spectrometer was used to time and spectrally resolve the emitted light and to determine graybody temperature histories with nanosecond time resolution. At 0.5 km s-1, first light emission was observed from Teflon, but at 0.6 km s-1, the emission from Al/Teflon became much more intense, so we assigned the impact threshold for Al/Teflon reactions to be 0.6 (±0.1) km s-1. The flyer plates produced a 7 ns duration steady shock drive. Emission from shocked Al/Teflon above threshold consisted of two bursts. At the higher impact velocities, the first burst started 15 ns after impact, peaked at 25 ns, and persisted for 75 ns. The second burst started at a few hundred nanoseconds and lasted until 2 μs. The 15 ns start time was exactly the time the flyer plate velocity dropped to zero after impact with sapphire. The first burst was associated with shock-triggered reactions and the second, occurring at ambient pressure, was associated with combustion of leftover material that did not react during shock. The emission spectrum was found to be a good fit to a graybody at all times, allowing temperature histories to be extracted. At 25 ns, the temperature at 0.7 km s-1 and the one-fourth Al load was 3800 K. Those temperatures increased significantly with impact velocity, up to 4600 K, but did not increase as much with Al load. A steady combustion process at 2800 (±100) K was observed in the microsecond range. Finally, the minimal dependence on Al loading indicates that these peak temperatures arise primarily from Al nanoparticles reacting almost independently, since the presence of nearby heat sources had little influence on the peak temperatures.},
doi = {10.1063/1.4977109},
journal = {Journal of Applied Physics},
number = 8,
volume = 121,
place = {United States},
year = {Tue Feb 28 00:00:00 EST 2017},
month = {Tue Feb 28 00:00:00 EST 2017}
}

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Works referenced in this record:

Thermal imaging of nickel-aluminum and aluminum-polytetrafluoroethylene impact initiated combustion
journal, October 2012

  • Densmore, John M.; Biss, Matthew M.; Homan, Barrie E.
  • Journal of Applied Physics, Vol. 112, Issue 8, Article No. 084911
  • DOI: 10.1063/1.4762009