<p>Future energy systems based on hydrogen as energy carrier require reliable ways for storing hydrogen gas in safe, clean and efficient ways. Metal hydrides absorb hydrogen gas reversibly, making them suitable for storage applications. Investigations of the crystal structures of these materials contribute to an understanding of the factors which can influence the absorption<i>. </i></p><p>Three systems, Ti<sub>3</sub>Sn-D, Nb<sub>4</sub>MSi-D (M=Co or Ni) and Pd-Ni-P, have been investigated in this thesis. Various solid state synthesis techniques have been used for sample preparation. The crystal structures have been studied using x-ray and neutron diffraction techniques.</p><p>Three metal hydride phases were found in the Ti<sub>3</sub>Sn-D system upon hydrogenation. Deuterium occupies titanium octahedra and the applied deuterium pressure induces the phase transitions. The distances between the deuterium atoms increase from 2.47 Å in orthorhombic Ti<sub>3</sub>SnD<sub>0.80</sub> to 4.17 Å in cubic Ti<sub>3</sub>SnD.</p><p>The Nb<sub>4</sub>MSi-D system (M=Co or Ni) readily absorbs deuterium at room temperature and 90 kPa deuterium pressure to give a deuterium content of Nb<sub>4</sub>MSiD<sub>~2.5</sub>. Two interstitial voids, both coordinated by four niobium atoms arranged in a tetrahedral configuration, accommodate deuterium atoms. </p><p>Two ternary phases and a solid solution of nickel in Pd<sub>3</sub>P have been synthesised and the crystal structures determined. PdNi<sub>2</sub>P is orthorhombic and crystallises in the MgCuAl<sub>2</sub>-type structure: an ordered derivative of the Re<sub>3</sub>B-type structure. Pd<sub>8</sub>Ni<sub>31</sub>P<sub>16</sub> is a tetragonal high-temperature phase stable at 700°C with 110 atoms in the unit cell. Pd<sub>2.7</sub>Ni<sub>0.3</sub>P<sub>0.94</sub> has the cementite-type structure with mixed occupancy of palladium and nickel at one of the two non-equivalent crystallographic metal positions.</p>
| Identifer | oai:union.ndltd.org:UPSALLA/oai:DiVA.org:uu-3466 |
| Date | January 2003 |
| Creators | Vennström, Marie |
| Publisher | Uppsala University, Department of Materials Chemistry, Uppsala : Acta Universitatis Upsaliensis |
| Source Sets | DiVA Archive at Upsalla University |
| Language | English |
| Detected Language | English |
| Type | Doctoral thesis, comprehensive summary, text |
| Relation | Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, 1104-232X ; 846 |
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