"Ignition Mechanisms of Reactive Nanocomposite Powders Combining Al, B," by Siva Kumar Valluri, Mirko Schoenitz et al.
 

Ignition Mechanisms of Reactive Nanocomposite Powders Combining Al, B, and Si as Fuels with Metal Fluorides as Oxidizers

Document Type

Article

Publication Date

1-1-2023

Abstract

Micron-sized nanocomposite powders combining 50 wt% of Al, B, or Si as fuels with a metal fluoride, specifically BiF3, CoF2, or NiF2, were prepared by arrested reactive milling. The reactions occurring upon heating such composite powders in both inert and oxidizing environments were studied using thermal analysis. Reaction products were collected at different temperatures and examined using electron microscopy and x-ray diffraction. Prepared composites were coated on an electrically heated filament for ignition experiments in air. Fluorination substantially accelerates oxidation for all fuels in the prepared composites heated in an oxidizing environment. Respectively, ignition temperatures are substantially reduced compared to those of fuel powders. For all composites with BiF3 as oxidizer, ignition is rate-limited by its thermal decomposition. Thermal decomposition of other fluorides rate-limits ignition for boron and silicon, for which the fluorination products are volatile. For Al-based materials, a condensed AlF3 layer forms prior to ignition, and diffusion through this layer limits the rate of reaction. For boron coated with boric acid, the fluorination is catalyzed by release of water upon heating, occurring at lower temperature than other reactions.

Identifier

85113240736 (Scopus)

Publication Title

Combustion Science and Technology

External Full Text Location

https://doi.org/10.1080/00102202.2021.1968845

e-ISSN

1563521X

ISSN

00102202

First Page

597

Last Page

618

Issue

3

Volume

195

Grant

HDTRA12020001/2004756624

Fund Ref

Office of Naval Research

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