Influence of Aluminum Passivation on the Reaction Mechanism: Flame Propagation Studies
TEXAS TECH UNIV LUBBOCK DEPT OF MECHANICAL ENGINEERING
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Currently, two main known mechanisms of aluminum Al nanoparticle reaction are discussed in the literature, namely those based on diffusion through an oxide shell and melt-dispersion. The two mechanisms lead to opposite predictions in nanoparticle design. The diffusion mechanism suggests that the reduction or complete elimination of the oxide shell will increase Al reactivity, whereas the melt-dispersion mechanism suggests an increase in initial oxide thickness up to an optimal value. The goal of this study is to perform critical experiments in a confined flame tube apparatus to compare these two predictions. Specifically, the flame propagation rates of perfluoroalkyl carboxylic acid Cl3F27COOH-treated Al nanoparticles with and without an alumina shell were measured. Results show that when there is no alumina passivation shell encasing the Al core, the flame rate decreases by II factor of 22-95 and peak pressure deceases by 3 orders of magnitude, in comparison with the AI particles with an oxide shell. These results imply that the melt-dispersion reaction mechanism is responsible For high flame propagation rates observed in these confined tube experiments.
- Physical Chemistry