Frontiers in Materials (Feb 2020)
Thermo-Mechanical Stability and Gas-Tightness of Glass-Ceramics Joints for SOFC in the System MgO-BaO/SrO-B2O3-SiO2
Abstract
The objective of this paper is to illustrate a variety of studies carried out to improve the quality of some particular glass-ceramic joining materials based on measured properties such as gas-tightness and mechanical resistance and demonstrate the feasibility of using the proposed materials for solid oxide fuel cells (SOFC) and solid oxide electrolysis cells (SOEC) applications. First, the sealing conditions have been optimized for the two selected compositions in the system MgO-BaO/SrO-B2O3-SiO2. Once the joining materials have been optimized, the gas-tightness has been measured as a function of the glass-ceramic crystallization degree, its thermal cycling behavior and the influence of a reducing atmosphere on this property. The electrical resistance at high temperature has also been studied. Subsequently, the chemical compatibility of the joints steel/glass-ceramic has been evaluated by means of the analysis of the cross-sections using SEM and EDX. Furthermore, the mechanical and chemical stability of the joints has also been studied as a function of the crystallization degree, the resistance vs. thermal cycling and the influence of a reducing atmosphere. Finally, the mechanical resistance of the joints regarding flexural loading has been characterized employing a 4-point bending method both at room temperature and at relevant high temperatures varying the seal thickness. Overall, the results verify that the developed and tested materials are promising for long term stable SOFC and SOEC applications in advanced stack designs aiding prolonged lifetime under thermal-cyclic conditions.
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