Thesis (M.S.)--Rochester Institute of Technology, 2009. / Typescript. Includes bibliographical references (leaves 74-78).

A numerical model for solid oxide fuel cells with Ni-infiltrated porous anode has been described. The novel contribution of the work is the development of a semi-continuous film model to describe the infiltrated Ni-phase. This model relates experimentally controllable parameters, namely, Ni- loading, porosity and pore size to the effective electronic conductivity of the Ni-phase and the number of active reaction sites or the triple phase boundary (TPB). The semi-continuous film model was incorporated in a two-dimensional (2D) SOFC model. The 2D model considers the coupled gas-phase transport, charge transport and electrochemical kinetics to directly examine the effect of Ni loading and porosity on the electrochemical performance of Ni-infiltrated SOFC anodes. From the semi-continuous film model, an optimal Ni loading that corresponds to a maximum in TPB length was identified. Comparison of effective electronic conductivity and TPB length for a Ni-infiltrated anode with those for a composite Ni-YSZ anode suggests that an infiltrated Ni anode with adequate electrical conductivity and sufficiently high TPB length can be fabricated even at a very low Ni loading. Comparison of various porous anodes with varying Ni loading, it was determined that maximum electrochemical performance does indeed correspond to anode with maximum TPB length. It was also determined that an infiltrated anode will have higher performance capabilities when compared to the conventional composite electrodes. However, degradation of performance may result due to degradation of connectivity in the infiltrated Ni. The methodology to model the latter effect was also proposed. / Thesis (Master, Chemical Engineering) -- Queen's University, 2012-06-13 13:09:49.182

Thesis (M.S.)--Tennessee Technological University, 2009. / Title from title page screen (viewed on Aug. 25, 2009). Bibliography: leaves 68-71.

Thesis (Ph. D.)--Ohio State University, 2007. / Title from first page of PDF file. Includes bibliographical references (p. 75-77

Thesis (M.S)--Ohio University, March, 2005. / Title from PDF t.p. Includes bibliographical references (leaves 129-132)

Thesis (Ph. D.)--University of Alberta, 2010. / Title from pdf file main screen (viewed on July 2, 2010). A thesis submitted to the Faculty of Graduate Studies and Research in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Chemical Engineering, Department of Chemical and Materials Engineering, University of Alberta. Includes bibliographical references.

No description available.

The success of Solid Oxide Fuel Cells (S.O.F.C) rests heavily on material selection. The performances of several compounds were investigated as possible anode materials, starting with reduced titanates such as the magnesium titanate and zirconium titanate. These compositions, although possessing many qualities beneficial for use as an anode material, were found to be too unstable for practical use. For this reason further work concentrated on stable, zirconia based, compounds with exhibited mixed conduction under reducing atmospheres. The mobility of electronic carriers is considered to be much higher than that of ionic defects, therefore, promising mixed conductors can be formed by doping a good ionic conductor with a small concentration of transition metal ions. Zirconia based mixed conductors were studied for two reasons. Firstly, zirconia stabilised in the cubic defect fluorite structure, exhibits a high level of ionic conductivity. Secondly, it is the most common electrolyte material for an S.O.F.C. An anode based on zirconia would, therefore, be expected to offer a good physical compatibility with the electrolyte material and to exhibit a high ionic contribution to total conductivity. Large defect fluorite solid solutions in the systems Y<SUB>2</SUB>O<SUB>3</SUB>-ZrO<SUB>2</SUB>-Nb<SUB>2</SUB>O<SUB>5</SUB>, Yb<SUB>2</SUB>O<SUB>3</SUB>-ZrO<SUB>2</SUB>-Nb<SUB>2</SUB>O<SUB>5</SUB> and CaO-ZrO<SUB>2</SUB>-Nb<SUB>2</SUB>O<SUB>5</SUB> were established, which enabled the effects of composition, dopant size and charge on conduction to be investigated. These effects were shown to be linked to structure. From these results and comparisons with the Y<SUB>2</SUB>O<SUB>3</SUB>-ZrO<SUB>2</SUB>-TiO<SUB>2</SUB> system, optimum, mixed conducting, compositions were established. The sample Y<SUB>0.25</SUB>Ti<SUB>0.15</SUB>Zr<SUB>0.60</SUB>O<SUB>1.875</SUB> exhibited the best mixed conducting properties to date, obtained for compositions based on zirconia.

Thesis (M.S.)--Tennessee Technological University, 2009. / Title from title page screen (viewed on Feb. 5, 2010). Bibliography: leaves 93-100.

Solid oxide fuel cells (SOFCs) are power generation devices that offer many great advantages compared to lower temperature fuel cells; for example, they are able to operate at high efficiencies without the use of expensive precious metal catalysts, and are also able to directly utilize hydrocarbon fuels without the need of an external reformer. Unfortunately, the conventional high operating temperature of these devices (T ≈ 1000 °C) requires the use of expensive, specialized materials that can withstand these high temperatures. This issue has generated considerable interest in reducing the operating temperature of these devices to the intermediate-temperature (600 – 800 °C) to allow for the use of less-expensive materials, such as stainless steel. However, the conventionally utilized SOFC cathode materials exhibit poor electrochemical performance at these reduced temperatures. Currently considered alternative intermediate temperature cathodes, such as Ba₀.₅Sr₀.₅Co₀.₈Fe₀.₂O₃₋δ (BSCF), offer improved performance, but have a large thermal expansion coefficient (TEC), leading to cell failure. In light of these issues, this dissertation focuses on the development of low TEC cathodes for intermediate temperature SOFCS (IT-SOFCs). The primary focus of this dissertation is on the swedenborgite-type RBaCo₃MO₇₊δ (R = Y, In, and Ca; M = Zn and Fe) series of cathodes. Due to their tetrahedrally-coordinated M site, the cobalt ions in these materials do not undergo a spin-state transition, and have TECs similar to conventional SOFC electrolyte materials. The long-term phase stability of these materials was addressed, and it was discovered that a slight In substitution significantly promoted phase stability. In the Y₁₋[subscript x] In [subscript x] BaCo₃ZnO₇₊δ series, it was observed that x = 0.1 successfully stabilized the phase without observable degradation of performance. Similarly, a high-Ca content material (Y₀.₅In₀.₁Ca₀.₄BaCo₃ZnO₇₊δ) was successfully stabilized, though Ca is known to destabilize the phase; furthermore, this compound showed improved performance compared to YBaCo₃ZnO₇₊δ. Lastly, the replacement of the performance-inhibiting Zn with Fe was investigated, and the Y₀.₉In₀.₁BaCo₃Zn₀.₆Fe₀.₄O₇₊δ sample showed low temperature performance rivaling BSCF. Other work in this dissertation focuses on the application of functional silver materials for use in SOFCs, with good performance; these materials were easily manufactured, and they showed performance drastically greater than the conventionally utilized platinum. / text