Fabrication and reaction mechanism study of Co(OH)F@Al nanowire arrays: A functional fluorine-containing metastable intermolecular composite

Metastable intermolecular composites (MICs) comprising solid fuels and oxidizers at nano-scale exhibit high energy densities and fast reaction speeds. As most metal and metalloid fuels are passivated by the natural oxide layer on the surface which acts as a reaction barrier, fluorine-containing oxidizers are of particular interest to promote the reactivity through interfacial fluoridation. In this work, cobalt hydroxy fluoride (Co(OH)F) was introduced as a functional fluorine-containing oxidizer, and core-shell structured Co(OH)F@Al nanoarray was fabricated onto a glass substrate. The thermal behavior and reaction mechanism of pure Co(OH)F and Co(OH)F@Al composites were thoroughly investigated, and Co(OH)F@Al was compared with CoO@Al and Co 3 O 4 @Al with identical morphology. In the Co(OH)F@Al composite, a preignition reaction was observed which was attributed to the etching of Al 2 O 3 shell by HF and the fluoridation of Al core by HF and CoF 2 . With the assistance of pre-ignition reaction, Co(OH)F@Al can complete main exothermal reaction before Al melting in a solid-state mechanism, and its peak temperature is around 200 degrees C lower than those of MICs employing CoO and Co 3 O 4 as oxidizers.& COPY; 2023 The Combustion Institute. Published by Elsevier Inc. All rights reserved.

Automated summary

Metastable intermolecular composites (MICs) consisting of Co(OH)F@Al nanoarray were investigated for their thermal behavior and reaction mechanism. The results revealed that Co(OH)F@Al can undergo the main exothermal reaction before the melting of aluminum, achieving a peak temperature about 200 degrees C lower than MICs using CoO and Co3O4 oxidizers.