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Aluminum Cluster Based Materials for Propulsion and Other Applications

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Virginia Commonwealth University Richmond United States

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The key objective of our work has been to study the interaction of aluminum and aluminum based clusters with organic templates, with oxygen and water, and develop protocols that would enable the synthesis of cluster assembled materials based on reactive and non-reactive motifs. Our studies on the reactivity of aluminum clusters with propene showed that the reactivity was related to the location of the unoccupied molecular orbital and that clusters like Al12-, Al15-, Al18-, and Al21- can readily bind to propene and hence may be suitable building blocks to generate such materials. For Al13, a superhalogen superatom discovered by us, our studies showed that an ionic assembly composed of Al13 and super-alkali K3O is stable and ideal to generate an ionic solid. Through synergistic efforts combining theoretical studies in my group and experiments in A. W. Castlemans AWC group at PSU, we identified Al4H7- as a very stable species that is resistant to oxygen and ideal building blocks for cluster materials. We also showed that the reactive aluminum clusters can be made less reactive by adding H atoms as it changes the spin state of the system. We also established general protocols for using the findings on free clusters to generate cluster assembled materials and in collaboration with experimental groups, synthesized a cluster solid of As7K3 species through a directed chemical synthesis. Recently, in a synergistic efforts combining experiments in AWC group at PSU, we have discovered an unusual size dependent reactivity of aluminum cluster anions with water, in that Al16-, Al17-, and Al18- are found to produce hydrogen through processes linked to their geometries. The studies provide a new Approach to synthesize hydrogen from water, on demand, and have just been published in SCIENCE. We believe that these developments are important towards cluster based materials for propulsion and nanoenergetic applications.

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Technical Report,15 Mar 2005,30 Nov 2008



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Approved For Public Release;

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