Thesis (Ph. D.)--University of Hong Kong, 2010. / Includes bibliographical references (leaves 124-125). Also available in print.

Solid oxide fuel cells (SOFC), owing to its high operating temperatures, have many advantages over other types of fuel cells. Its commercialization, however, relies greatly on its costs and long term durability. By reducing the operating temperature to the intermediate temperature range, the costs for the balance of plant would be significantly reduced. The greatest contribution to cell over-potential at this temperature range is the oxygen reduction at cathode; hence development of a cathode material with low specific resistance and durability would have direct impact on the commercialization of SOFC. Composite cathode is a common strategy used by many to improve cathode performance. This was done conventionally by random mixing of cathode material with a better ionic conductor such as the electrolyte material. Impregnation or infiltration is often used to improve interconnectivity among individual phases in the composite, In this study, fabrication of a composite cathode with two phases - gadolinium doped ceria (GDC) and platinum attempted, forming two inter-locked networks each with a channel dimension in the nanometer range by hard templating and chemical vapor infiltration (CVI) both for the first time to the best of my knowledge. It was found that surface layer of these materials play a very important role in the performance and structural stability. Another set of composite cathode was fabricated by packing commercially available GDC with carbon pore-former following by impregnation with Pt/Ag-Pt alloy. By introducing small amount of silver (6wt%), area specific resistance of 0.94cm2 and 0.16cm2 were observed at 550C and 660C, respectively during impedance spectroscopy in symmetrical cell arrangement. Silver was proposed to provide greater effective surface area for surface exchange and extending the triple phase boundary. Platinum was also suggested to provide a surface where silver wetting is possible stabilizing morphology of silver in the GDC scaffold. Platinum is not a practical choice of electrode material due to its costs and lower performance, it was chosen to demonstrate the strategy of vapor phase infiltration in fabricating SOFC composite cathode. However, the technique of CVI demonstrated can potentially be applied to other cathode candidate materials. / published_or_final_version / Chemistry / Doctoral / Doctor of Philosophy

The decay properties of the neutron deficient nuclei $ sp{144}$Gd, $ sp{142}$Gd, $ sp{ rm 141g}$Gd, $ sp{ rm 141m}$Gd and $ sp{140}$Gd are investigated in detail for the first time and the new beta decaying isomers $ sp{ rm 141g,m}$Gd, $ sp{141}$Tb(A) and $ sp{140}$Gd are discovered. A gas-jet recoil-transport system and a conversion electron spectrometer are designed and constructed in order to measure the electromagnetic transitions emitted following their decay. Levels schemes are deduced for the daughter nuclei $ sp{144}$Eu, $ sp{142}$Eu, $ sp{141}$Eu, $ sp{140}$Eu, and $ sp{141}$Gd and spin-parity assignments are established for several states. The decay half-life of these nuclei is also measured. / The deduced information is discussed in the general context of the Z $ geq$ 50, N $ leq$ 82 mass region. The low lying structure of the N = 76, 77, 78, 79, 81 and 82 isotones is compared to the predictions of theoretical calculations using either spherical BCS or deformed Hartree-Fock plus BCS formalism with a semi-realistic interaction derived from the Tabakin potential. Contributions to original knowledge are outlined in Chapter V.

Thesis (Ph.D.)--University of Delaware, 2009. / Principal faculty advisor: George C. Hadjipanayis, Dept. of Physics & Astronomy. Includes bibliographical references.

Thesis (M.A.)-University of California, Berkeley, January 1957.

Mainz, Univ., Diss., 2000.

Universiẗat, Diss., 2004--Mainz.

Thesis (Ph.D.)--University of Nebraska-Lincoln, 2008. / Title from title screen (site viewed Feb. 17, 2009). PDF text: xiii, 110 p. : ill. ; 3 Mb. UMI publication number: AAT 3326861. Includes bibliographical references. Also available in microfilm and microfiche formats.

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