科研之友
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摘要
The present work combines X-ray diffraction (XRD) analysis and NMR Study of Na3-nLinAlH6 (n = 0, 1, 2) alanates synthesized by high-pressure reactive ball milling. Reactive ball-milling of alkali hydrides and Al Under it hydrogen pressure of 10 MN allows for the synthesis of Na3AlH6 and Na2LiAlH6 with a yield higher than 90 wt % When using 2 mol % of TiCl3 as a dopant The synthesis of NaLi2AlH6 compound by reactive ball Milling was not Successful The crystal Structure of both Na3AlH6 and Na2LiAlH6 phases are in agreement with previous publications. The phase compositions of the synthesized samples obtained from XRD analysis are in good agreement with the results determined from NMR refinements Without the addition of TiCl3, Na3AlH6 compound Could also be formed, although the reaction was not complete due to slow kinetics. For the magic angle spinning NMR Al-26, Na-23, Li-6, and H-1 spectra, strong bulk magnetic Susceptibility (BMS) effects have been observed to affect to the same extent all detected lines and thus indicates that paramagnetic species (Ti3+ or Ti-0 bearing phase) are present and well dispersed in the samples. Na-23 and Al-27 NMR spectra call be refined with very similar NMR parameters for both doped and nondoped samples, suggesting that Ti does not incorporate the crystal structure of these materials. Accurate values of Na-23 and Al-27 NMR parameters and quantification Of the studied phases have been obtained thanks to a new treatment allowing for taking into account the BMS effects. Finally, it good agreement of experimental Na-23 and Al-27 quadrupolar parameters with density functional theory using the gauge-including projector augmented wave (DFT-GIPAW) predicted values is obtained. This work validates the use of DFT-GIPAW calculations for future NMR studies.
- 出版日期2009-12-17
- 单位中国地震局
