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dc.contributor.advisorWalter, Mark E.
dc.creatorGatts, Timothy J.
dc.description.abstractSince the Industrial Revolution in the 19th Century, fossil fuels have been burned to produce power and heat. The inefficiency of the combustion process coupled with a dwindling supply of fossil fuels necessitates the need for new fuel sources and new methods for more efficient energy conversion. Solid Oxide Fuel Cells (SOFCs) are one of many emerging technologies that can help to replace fossil fuel combustion. SOFCs allow for the use of various hydrogen-rich fuels to produce electricity and waste heat. The only byproducts of SOFCs are water, heat, and sometimes carbon dioxide depending on the fuel, which are all safer than carbon monoxide given off in fossil fuel burning. The energy conversion method is much more efficient than fossil fuel combustion, and the byproducts are in general much cleaner and safer for humans and the environment. SOFCs are, however, still in development. One particular challenge for SOFCs is related to the need to isolate or seal the reductant (fuel) on the anode side and oxidant (oxygen) on the cathode side of each individual cell. Since they operate at high temperatures (700°C -1000°C), SOFCs are prone to failure due to thermal expansion mismatches between the various components. This project involves the investigation of three potential SOFC seal materials. The three seals are composed of 50% glass - 50% Zirconia, 75% glass - 25% Zirconia, and 100% glass. Each seal is used to create an annulus between two disks of Scandium-stabilized Zirconia (ScSZ) which is a ceramic used as an SOFCs electrolyte. The seal materials are also used to form an annulus between an ScSZ disk and a disk of crofer, a chromium-iron alloy commonly used for SOFCs interconnects. The seals are heated from room temperature to a typical SOFC operating temperature, held at operating temperature, and cooled back to room temperature. This temperature profile simulates the start-up, operation, and cool-down of an actual SOFC. The seals are tested for failure by Acoustic Emission (AE) analysis. The AE results are then verified using Finite Element Analysis (FEA) simulations. The experimental results are used to determine when in the thermal cycle seal failure occurs, and the FEA simulations are used to determine the most likely reason for failure and location of failure. The experimental results show that for all seal materials and all interfaces, significant seal degradation occurs during the cooling of the materials from high operating temperature to room temperature. For sealing ScSZ to ScSZ, the 100% glass seal is found to be the least prone to failure. For sealing ScSZ to crofer, the results are less clear cut. These results are characterized by critical time, tcr, which is defined by the time from the start of cooling until failure. Based on the analysis of tcr, all three seals fail, but 50% glass - 50% Zirconia has the largest tcr. These results indicate that using glass seals with a ceramic reinforcement is where future research should follow. After testing is complete, the seal materials remain attached to the ScSZ disk but have become detached from the crofer disk. Based on these results, the expected mode of failure is separation of the seal from the crofer. The FEA simulation results validate this observation. The stress at the seal/crofer interface is compressive during most of the heating stage. However, during the hold at operating temperature the stress becomes tensile, and during cooling the tensile stress increases. It can be inferred from the data that when the tensile stress reaches some threshold the bond between the glass seal and the ceramic disk will be broken, and the material will separate.en_US
dc.description.sponsorshipNexTech Materials, Ltd.en_US
dc.description.sponsorshipThe Ohio State University Office of Technology Enhanced Learning and Researchen_US
dc.description.sponsorshipThe Ohio State University College of Engineeringen_US
dc.publisherThe Ohio State Universityen_US
dc.relation.ispartofseriesThe Ohio State University. Department of Mechanical Engineering Honors Theses; 2008en_US
dc.subjectacoustic emissionen_US
dc.subjectglass sealen_US
dc.subjectfinite element analysisen_US
dc.titleInvestigation of the Heating and Cooling of Composite Glass Seals for SOFCsen_US
dc.description.embargoNo embargoen_US
dc.rights.ccAttribution-NonCommercial-ShareAlike 3.0 Unporteden_US

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