Abstract
Surface-mediated Al particles are synthesized by incorporating the stable fluoride reaction of Al-F on a pure Al surface in place of natural oxides. Al particles with fluoro-polymer directly adsorbed on the surface show a considerable capability to overcome limitations caused by the surface oxide. Here, we report that Al fluoride when spontaneously formed at the poly(vinylidene fluoride)/Al interface serves as an oxidation-protecting layer while also providing an efficient combustion path along which the internal Al rapidly reacts with external oxygen atoms. Both thermal oxidation and explosion tests of the poly(vinylidene fluoride)/Al particles show superior exothermic enthalpy energy and simultaneously rapid oxidation reactivity compared to those of Al2O3 passivated Al particles. It is clearly elucidated that the enhanced energetic properties of Al particles mediated by poly(vinylidene fluoride) originate from the extraordinary pyrolytic process of Al fluoride occurring at a low temperature compared to Al2O3 passivated Al. Hence, these results clarify that the surface mediation of Al particles can be significantly considered as advanced technology for many energetic applications.
Highlights
As Chung et al and Crouse et al reported, hydrocarbon-based polymers have been investigated for passivating Al particles owing to the feasibility of the coating process as well as the achievement of suitable reactivity[13, 16]
Because poly(vinylidene fluoride) (PVDF) feasibly swells in an organic solvent, it can be effectively utilized as a molecular-coating agent in the solution compared to the nanoparticle-based polymers such as PTFE suspension[20, 28]
The structure of the PVDF layer introduced instead of the surface oxide is analyzed by focusing on the PVDF-coated Al (PVDF/Al) interface, and the oxidation-mechanism compared to that of Al2O3 passivated Al particles is suggested
Summary
Surface-mediated Al particles are synthesized by incorporating the stable fluoride reaction of Al-F on a pure Al surface in place of natural oxides. We report that Al fluoride when spontaneously formed at the poly(vinylidene fluoride)/Al interface serves as an oxidation-protecting layer while providing an efficient combustion path along which the internal Al rapidly reacts with external oxygen atoms Both thermal oxidation and explosion tests of the poly(vinylidene fluoride)/Al particles show superior exothermic enthalpy energy and simultaneously rapid oxidation reactivity compared to those of Al2O3 passivated Al particles. Once the internal Al material is continuously exposed as fluorine-compounds are formed and evaporated, the oxidation reaction proceeds efficiently compared to that with pure Al particles with a dense surface oxide that inhibits continuous combustion[25, 26] In this way, polymer materials composed of a carbon backbone with hydrogen and fluorine atoms has been studied as advanced passivation materials for pure Al particles. The structure of the PVDF layer introduced instead of the surface oxide is analyzed by focusing on the PVDF/Al interface, and the oxidation-mechanism compared to that of Al2O3 passivated Al particles is suggested
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