Al K Edge XANES Measurements in NaAlH4 Doped with TiCl3 by Ball Milling

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• 作者：Aline L&eacute ; on ; Antonella Balerna ; Gianfelice Cinque ; Christoph Frommen ; Maximilian Fichtner
• 刊名：Journal of Physical Chemistry C
• 出版年：2007
• 出版时间：March 8, 2007
• 年：2007
• 卷：111
• 期：9
• 页码：3795 - 3798
• 全文大小：53K
• 年卷期：v.111,no.9(March 8, 2007)
• ISSN：1932-7455

文摘

Al K edge X-ray absorption spectroscopy has been applied to investigate pure sodium alanate and sodiumalanate doped with 5 mol % Ti on the basis of TiCl₃ by ball milling. These first experimental data indicatethat the chemical state of Al in NaAlH₄ does not change upon cycling. It confirms also that the valence stateof Al is higher than that of metallic Al in NaAlH₄. Moreover, a change in the orbital occupancy of Al atomsor structural disorder in the local Al surroundings is occurring most probably after doping sodium alanateand subsequent cycling under hydrogen. Indeed, an evolution of the X-ray absorption near-edge structure(XANES) features can be observed with increasing number of cycles under hydrogen compared to the purealanate sample. After several cycles, a new phase containing metallic Al is formed, which corresponds to themixture of Al and the formation of small Ti-Al clusters already observed in Ti K edge measurements. Thesepreliminary results suggest the presence of molecular-scale inhomogeneities within the average structure ofsodium alanate.