"Low-Temperature Exothermic Reactions in Al/CuO Nanothermites Producing" by Mehnaz Mursalat, Ci Huang et al.
 

Low-Temperature Exothermic Reactions in Al/CuO Nanothermites Producing Copper Nanodots and Accelerating Combustion

Document Type

Article

Publication Date

4-23-2021

Abstract

Several Al/CuO nanocomposite reactive materials, prepared recently by arrested reactive milling, were found to exhibit a distinct low-temperature exothermic peak around 600 K seen by differential scanning calorimetry. This work is an experimental study aimed to establish whether this low-temperature reaction affects combustion and why it is observed in some but not all materials with identical compositions. The peak is only observed when aluminum is initially separately milled in acetonitrile. Electron microscopy showed resulting composite powders to be porous, unlike fully dense powders obtained without premilling aluminum. The as-prepared and partially reacted powders recovered after heating just past the peak to 650 K were examined using high-angle annular dark-field scanning transmission electron microscopy and electron energy loss spectroscopy. Additionally, X-ray diffraction measurements were performed for all materials. Finally, the reactive powders were ignited using plasma and shock generated by an electrostatic discharge. Results show that the low-temperature exothermic peak is associated with a redox reaction pathway involving release of oxygen by CuO that is not in direct contact with Al and free-molecular transport of that oxygen to the nearby surface of Al. This reaction pathway inhibits the formation of Al/Cu intermetallic phases. Instead, nanometer-scale metallic Cu particles are formed due to CuO reduction. It is also found that this reaction pathway accelerates ignition of reactive powders, which in turn leads to a higher burn rate of aerosolized powder.

Identifier

85103774035 (Scopus)

Publication Title

ACS Applied Nano Materials

External Full Text Location

https://doi.org/10.1021/acsanm.1c00236

e-ISSN

25740970

First Page

3811

Last Page

3820

Issue

4

Volume

4

Grant

HDTRA12020001/2004756624

Fund Ref

Defense Threat Reduction Agency

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