Glass-ceramics for solid oxide fuel cell seals

<p>"This dissertation is comprised of five sections. The first section includes a review of the literature on the development of glass and glass-ceramic sealants for solid oxide fuel cells (SOFC), including the critical issues for sealant design. Section two describes a quantitative approach to characterize the isothermal crystallization of glass using differential thermal analysis (DTA)<strong>, </strong>with Li₂O-2SiO₂ as the model system. Section three applies this approach using a SOFC sealing glass (glass#27). The finer powder crystallizes much faster than larger particles and the addition of a second phase filler also increases the crystallization rate of the base glass. Surface crystallization dominates in this glass system. Section four includes the quantitative study of reactions between sealing glass and Cr₂O₃ to understand the formation of deleterious chromate phases. The formation of detrimental phases such as SrCrO₄ at the interface between glass-ceramic sealants and stainless steel interconnects depends on the heat treatment temperature, time and atmosphere. It<strong> </strong>was also found that the formation of SrCrO₄ is affected by the addition of ZnO to the sealing glass due to the competing formation of ZnCr₂O₄. Section five describes the volatility of B₂O₃ from sealing glasses under SOFC operational conditions. Based on thermodynamic analyses, B₂O₃ is the most volatile of all oxide components in sealing glasses. The volatility of B₂O3 from the glass depends on the atmosphere, time, temperature and B₂O₃ activity. An increase in mass loss with increasing time at higher temperature in air was observed. The relationship between glass composition and properties are summarized in the appendix. The addition of B₂O₃ and ZnO decreases glass transition temperature of glasses and thus improves the glass forming tendency. The addition of B₂O₃ also decreases the softening temperature of glasses. The coefficient of thermal expansion of glasses depends on the average field strength of alkaline earth oxides"--Abstract, page iv.</p>

Name thesis:degree_name

Ph. D. in Ceramic Engineering

Grantor

Missouri University of Science and Technology

Year dc:date.available

2016

Author dc:creator

• Zhang, Teng

• Ceramic Materials

Repository record dc:identifier

https://scholarsmine.mst.edu/doctoral_dissertations/1766

OAI identifier oai:identifier

oai:scholarsmine.mst.edu:doctoral_dissertations-2768