Doctoral Dissertations

Abstract

"The relationships between the processing parameters, microstructures and electrochemical performance of solid oxide fuel cell (SOFC) components were investigated. The operating regimes (i.e., reducing vs. oxidizing) as well as the elevated temperatures (e.g. 800°C) for their operation introduce several material challenges. Therefore, composite materials are employed to withstand operating conditions while providing sufficient electrochemical performance for fuel cell operation. Analyses on lanthanum-strontium manganite (LSM) - yttria stabilized zirconia (YSZ) compositions (45 vol%-55 vol%) by impedance spectroscopy demonstrated that two competing polarization mechanisms (i.e. charge-exchange and surface adsorption-diffusion of oxygen) limit performance. Optimization of microstructures resulted in total resistances as low as 0.040 Ohm cm². Studies on Ag composites revealed that incorporation of up to 25 vol% oxide particles (LSM and YSZ) with sizes comparable to the Ag grains (~0.5 μm) can minimize the densification and coarsening of the Ag matrix. While the powder based oxide additions increased the stability limit of porous Ag composites from <550°C to 800°C, the use of nanostructured coatings increased the stability limit to 900°C for cathodes and current collectors. Investigations of Ni-YSZ anode microstructures demonstrated that uniform distribution of percolating isometric pores (>5 μm) allows forming desired continuous percolation of all phases (Ni, YSZ and pores) lowering activation polarization below 0.100 Ohm cm² and maintaining significant electrical conductivity (>1000 S/cm). Identification of polarization mechanisms by deconvolution of impedance spectra and tailoring the corresponding microstructures was demonstrated as an effective method for optimization of SOFC components"--Abstract, page v.

Advisor(s)

Dogan, Fatih

Committee Member(s)

Huebner, Wayne
Fahrenholtz, William
OKeefe, Matt
Xing, Yangchuan

Department(s)

Materials Science and Engineering

Degree Name

Ph. D. in Materials Science and Engineering

Publisher

Missouri University of Science and Technology

Publication Date

Spring 2013

Journal article titles appearing in thesis/dissertation

  • Influence of microstructural evolution on the electrochemical performance of LSM-YSZ composite cathodes for high performance solid oxide fueld cells.
  • Silver composites as highly stable cathode current collectors for solid oxide fuel cells.
  • Silver based perovskite nanocomposites as combined cathode and current collector layers for solid oxide fuel cells.
  • Effect of various pore formers on the microstructural development of tape-cast porous ceramics.
  • Development of anode pore structure and its effects on the performance of solid oxide fuel cells.

Pagination

xiv, 224 pages

Note about bibliography

Includes bibliographical references.

Rights

© 2013 Ayhan Sarikaya, All rights reserved.

Document Type

Dissertation - Open Access

File Type

text

Language

English

Library of Congress Subject Headings

Solid oxide fuel cells
Fuel cells -- Analysis
Metallic oxides -- Microstructure
Composite materials

Thesis Number

T 10317

Electronic OCLC #

853281118

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