Experimental investigation of the biaxial flexural strength of 8YSZ thin film ceramic substrates as electrolytes

Persistent Link:
http://hdl.handle.net/10150/279958
Title:
Experimental investigation of the biaxial flexural strength of 8YSZ thin film ceramic substrates as electrolytes
Author:
Cheng, Ming
Issue Date:
2002
Publisher:
The University of Arizona.
Rights:
Copyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.
Abstract:
Thin ceramic substrates are widely used in engineering applications in modern industry. For example, they are used as molecular filters in fuel cells and solid oxide electrolyzers for oxygen generation. Development of high-reliability substrate materials inevitably requires the accurate characterization of their mechanical properties. The loading conditions in service on the ceramic substrates, such as the solid oxide electrolytes with a thickness of much less than 2 mm, often involve multiaxial bending instead of simple tension or bending. In this dissertation, the ASTM standard piston-on-3-ball experimental technique at ambient temperature is employed to investigate the quasi-static biaxial flexural strength of pure 8YSZ and Al₂O₃ or 3YSZ doped 8YSZ ceramic substrates. Furthermore, this piston-on-3-ball experimental technique is developed into a dynamic piston-on-3-ball technique at ambient temperature and a quasi-static piston-on-3-ball technique at elevated temperatures. Stress distribution functions in the tensile surface of a specimen under piston-on-3-ball loading condition are formulated and used to develop statistical models, which are proven to be in the form of a Weibull distribution function, to describe the biaxial flexural strength behavior of ceramic substrates under piston-on-3-ball loading condition. Analytical modeling was conducted on the dynamic piston-on-3-ball loading configuration. This analytical model can be used to guide the experimental design and judge the validity of experimental results. A new material constitutive model is developed to give a good description of the dynamic strength behavior of ceramic materials under constant stress-rate loading. Quasi-static experiments under piston-on-3-ball loading are conducted at both ambient temperature and elevated temperatures, while dynamic experiments are conducted at ambient temperature. Experimental results, as well as observations from SEM microstructure images and values of fracture toughness measured using a newly developed Vickers micro-indentation toughness technique, lead to a conclusion that no obvious overall improvement to the SYSZ ceramic substrates in the biaxial flexural strength can be observed by adding Al₂O₃ additive with amount up to 3 mol% or 3YSZ additive with amount up to 30 wt%.
Type:
text; Dissertation-Reproduction (electronic)
Keywords:
Engineering, Mechanical.; Engineering, Materials Science.
Degree Name:
Ph.D.
Degree Level:
doctoral
Degree Program:
Graduate College; Aerospace and Mechanical Engineering
Degree Grantor:
University of Arizona
Advisor:
Chen, Weinong (Wayne)

Full metadata record

DC FieldValue Language
dc.language.isoen_USen_US
dc.titleExperimental investigation of the biaxial flexural strength of 8YSZ thin film ceramic substrates as electrolytesen_US
dc.creatorCheng, Mingen_US
dc.contributor.authorCheng, Mingen_US
dc.date.issued2002en_US
dc.publisherThe University of Arizona.en_US
dc.rightsCopyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.en_US
dc.description.abstractThin ceramic substrates are widely used in engineering applications in modern industry. For example, they are used as molecular filters in fuel cells and solid oxide electrolyzers for oxygen generation. Development of high-reliability substrate materials inevitably requires the accurate characterization of their mechanical properties. The loading conditions in service on the ceramic substrates, such as the solid oxide electrolytes with a thickness of much less than 2 mm, often involve multiaxial bending instead of simple tension or bending. In this dissertation, the ASTM standard piston-on-3-ball experimental technique at ambient temperature is employed to investigate the quasi-static biaxial flexural strength of pure 8YSZ and Al₂O₃ or 3YSZ doped 8YSZ ceramic substrates. Furthermore, this piston-on-3-ball experimental technique is developed into a dynamic piston-on-3-ball technique at ambient temperature and a quasi-static piston-on-3-ball technique at elevated temperatures. Stress distribution functions in the tensile surface of a specimen under piston-on-3-ball loading condition are formulated and used to develop statistical models, which are proven to be in the form of a Weibull distribution function, to describe the biaxial flexural strength behavior of ceramic substrates under piston-on-3-ball loading condition. Analytical modeling was conducted on the dynamic piston-on-3-ball loading configuration. This analytical model can be used to guide the experimental design and judge the validity of experimental results. A new material constitutive model is developed to give a good description of the dynamic strength behavior of ceramic materials under constant stress-rate loading. Quasi-static experiments under piston-on-3-ball loading are conducted at both ambient temperature and elevated temperatures, while dynamic experiments are conducted at ambient temperature. Experimental results, as well as observations from SEM microstructure images and values of fracture toughness measured using a newly developed Vickers micro-indentation toughness technique, lead to a conclusion that no obvious overall improvement to the SYSZ ceramic substrates in the biaxial flexural strength can be observed by adding Al₂O₃ additive with amount up to 3 mol% or 3YSZ additive with amount up to 30 wt%.en_US
dc.typetexten_US
dc.typeDissertation-Reproduction (electronic)en_US
dc.subjectEngineering, Mechanical.en_US
dc.subjectEngineering, Materials Science.en_US
thesis.degree.namePh.D.en_US
thesis.degree.leveldoctoralen_US
thesis.degree.disciplineGraduate Collegeen_US
thesis.degree.disciplineAerospace and Mechanical Engineeringen_US
thesis.degree.grantorUniversity of Arizonaen_US
dc.contributor.advisorChen, Weinong (Wayne)en_US
dc.identifier.proquest3050320en_US
dc.identifier.bibrecord.b42724120en_US
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