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Incomplete reactions in nanothermite composites

Published

Author(s)

Rohit J. Jacob, Diana Ortiz-Montalvo, Kyle R. Overdeep, Timothy P. Weihs, Michael R. Zachariah

Abstract

Exothermic reactions between oxophilic metals and transition/ post transition metal-oxides have been well documented owing to their fast reaction time scales (~10 μs). This article examines the extent of reaction in nano-aluminum based thermite systems through a forensic inspection of the products formed during reaction. Three nanothermite systems (Al/CuO, Al/Bi2O3 and Al/WO3) were selected owing to their diverse combustion characteristics thereby providing sufficient generality and breadth to the analysis. Microgram quantities of the sample were coated onto a fine platinum wire, which was resistively heated at high heating rates (~105 K/s) to ignite the sample. The subsequent products were captured/quenched very rapidly (~300 μs) in order to preserve the chemistry/morphology during initiation and subsequent reaction and were quantitatively analyzed using electron microscopy, Focused Ion Beam cross-sectioning followed by Energy Dispersive X-ray Spectroscopy. Elemental examination of the cross-section of the quenched particles show oxygen predominantly localized in the regions containing aluminum, implying the occurrence of redox reaction. The Al/CuO system, which has simultaneous gaseous oxygen release and ignition (TIgnition ≈ TOxygen Release), shows substantially lower oxygen content within the product particles as opposed to Al/Bi2O3 and Al/WO3 thermites, which are postulated to undergo a condensed phase reaction (TIgnition
Citation
Journal of Applied Physics
Volume
121

Keywords

Nanothermite, FIB, product analysis, condensed phase
Created February 3, 2017, Updated November 10, 2018