INOR 778 |
| Clathrates constitute unique class of inclusion compounds. Their very rich crystal chemistry, allows for a variety of physical properties such as thermoelectricity, superconductivity, and hydrogen storage abilities. Thermoelectric applications have been focused on inorganic clathrates (type I and II) in which group 14 elements make the cage structure and alkali metals are at the guest sites. Hydrogen storage applications have been primarily on type II clathrate hydrates in which H2O molecules comprise the cage structure with H2 molecules at the guest sites. One of the advantages of inorganic clathrate compounds over the clathrate hydrates is their stability under ambient atmosphere. This work describes the characterization of the new type-I Si clathrates, Na4(H2)2Si46, that encapsulates hydrogen at ambient temperature and pressure. This compound was prepared from the reaction between NaSi and NH4X (X = Cl and Br) under dynamic vacuum at 300 ºC. Rietveld refinement of powder X-ray diffraction data is consistent with the clathrate type-I structure. Solid-state 1H, 29Si and 23Na MAS NMR confirmed the presence of both hydrogen and sodium in the clatharte cages. To further investigate sodium occupancy, the synthesized particles were examined using spherical aberration (Cs) corrected VG H501 scanning transmission electron microscopy (STEM) operated at 100 kV. |
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Main Group Chemistry
9:00 AM-12:20 PM, Wednesday, August 22, 2007 BCEC -- 205C, Oral
Division of Inorganic Chemistry |