Atomic Scale Insights into the First Reaction Stages Prior to Al/CuO Nanothermite Ignition: Influence of Porosity

Document Type

Article

Publication Date

6-29-2022

Abstract

This theoretical work aims to understand the influence of nanopores at CuO-Al nanothermite interfaces on the initial stage of thermite reaction. ReaxFF molecular dynamics simulations were run to investigate the chemical and structural evolution of the reacting interface between the fuel, Al, and oxidizer, CuO, between 400 and 900 K and considering interfaces with and without a pore. Results show that the initial alumina layer becomes enriched with Al and grows primarily into the Al metal at higher temperatures. The modification of alumina is driven by simultaneous Al and O migration between metallic Al and the native amorphous Al2O3 layer. However, the presence of a pore significantly affects the growth kinetics and the composition of this alumina layer at temperatures exceeding 600 K, which impacts the initiation properties of the nanothermite. In the system without a pore, where Al is in direct contact with CuO, a ternary aluminate layer, a mixture of Al, O, and Cu, is formed at 800 K, which slows Al and O diffusion, thus compromising the nanothermite reactivity in fully dense Al/CuO composites. Conversely, the presence of a pore between Al and CuO promotes Al enrichment of the alumina layer above 600 K. At that temperature, any free oxygen molecules in the pore become attached to the reactive alumina surface resulting in a rapid oxygen pressure drop in the pore. This is expected to accelerate the reduction of the adjacent CuO as observed in experiments with Al/CuO composites with porosity at the CuO-Al interfaces.

Identifier

85133147849 (Scopus)

Publication Title

ACS Applied Materials and Interfaces

External Full Text Location

https://doi.org/10.1021/acsami.2c07069

e-ISSN

19448252

ISSN

19448244

PubMed ID

35699731

First Page

29451

Last Page

29461

Issue

25

Volume

14

Grant

832889

Fund Ref

Horizon 2020 Framework Programme

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