Date of Award

1-1-2012

Document Type

Campus Access Thesis

Department

Mechanical Engineering

First Advisor

David Ortiz

Abstract

There has been increasing interest in clean renewable energy generation for alternative use to traditional fossil fuels. Solid oxide fuel cells (SOFCs) have been at the forefront of this technology and are considered one of the promising technologies in this area. SOFCs ability to operate on hydrogen or hydrocarbon fuels makes them highly attractive. The current work devoted to the SOFC focuses on understanding it fundamentally in both fuel cell mode for power generation and electrolysis mode for fuel production. The focus on SOFCs has produced exciting novel fabrication techniques that can provide distinct advantages within the fuel cell.

This work concentrates on the novel freeze tape casting technique, which was developed as a direct mean of forming and controlling complex pore structures in ceramic materials. The work conducted in this paper focuses on the fundamental aspects of freeze tape casting to understand the variables involved with this process. Electrochemical testing is performed to validate this method and its ability to produce high performing SOFCs. The microstructure and electrochemical properties were investigated. Using various methods to investigate the microstructure, an acicular porous structure has been obtained using this method at differing porosities. The electrochemical performance, using these substrates, has shown power densities as high as 1.28 Wcm-2at 800°C. These freeze tape cast scaffolds have also shown significant reductions in polarization resistances (Rp). A cell employing a Ni-YSZ delivery layer, Ni-YSZ functional layer (FL), YSZ electrolyte, and LSM cathode displayed Rp of 0.56, 0.29, and 0.16 cm2at 700, 750 and 800°C, respectively.

Using freeze tape casting, the cell performance has been significantly improved by employing the novel acicular structure, due to dramatically decreased polarization resistance. However, mass transport limitation has been observed, particularly in electrolysis. The novel structure also improves mass transport further validating the novel freeze tape casting technique.

Rights

© 2012, Jacob Bunch

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