Development and characterization of glass-ceramic sealants in the (CaO–Al2O3–SiO2–B2O3) system for Solid Oxide Electrolyzer Cells

• Published in: Journal of power sources 2012-10, Vol.216, p.227-236
• Main Authors: Khedim, Hichem, Nonnet, Hélène, Méar, François O.
• Format: Article
• Language: English
• Subjects: Applied sciences; Crystallization; Differential thermal analysis; Direct energy conversion and energy accumulation; Electrical engineering. Electrical power engineering; Electrical power engineering; Electrochemical conversion: primary and secondary batteries, fuel cells; Energy; Energy. Thermal use of fuels; Equipments for energy generation and conversion: thermal, electrical, mechanical energy, etc; Exact sciences and technology; Fuel cells; Glass; Glass ceramics; Glass-ceramic; Heat treatment; Metal–glass interface; Sealers; Sealing materials; Solid Oxide Electrolyzer Cell (SOEC); Titanium dioxide; Yttria stabilized zirconia
• ISSN: 0378-7753; 1873-2755
• DOI: 10.1016/j.jpowsour.2012.05.041

The efficiency of glass-ceramic sealants plays a crucial role in Solid Oxide Electrolyzer Cell performance and durability. In order to develop suitable sealants, operating around 800 °C, two parent glass compositions, CAS1B and CAS2B, from the CaO–Al2O3–SiO2–B2O3 system were prepared and explored. The thermal and physicochemical properties of the glass ceramics and their crystallization behavior were investigated by HSM, DTA and XRD analyses. The microstructure and chemical compositions of the crystalline phases were investigated by microprobe analysis. Bonding characteristic as well as chemical interactions of the parent glass with yttria-stabilized zirconia (YSZ) electrolyte and ferritic steel-based interconnect (Crofer®) were also investigated. The preliminary results revealed the superiority of CAS2B glass for sealing application in SOECs. The effect of minor additions of V2O5, K2O and TiO2 on the thermal properties was also studied and again demonstrated the advantages of the CAS2B glass composition. Examining the influence of heat treatment on the seal behavior showed that the choice of the heating rate is a compromise between delaying the crystallization process and delaying the viscosity drop. The thermal Expansion Coefficients (TEC) obtained for the selected glass ceramic are within the desired range after the heat treatment of crystallization. The crystallization kinetic parameters of the selected glass composition were also determined under non-isothermal conditions by means of differential thermal analysis (DTA) and using the formal theory of transformations for heterogeneous nucleation. ► New glass-ceramic formulation for sealing applications. ► Influence of heat treatment on the seal behavior and crystallization process. ► Glass-ceramic/Metal and glass-ceramic/ceramic interfaces and interactions. ► Effect of V2O5, K2O and TiO2 on thermal properties. ► Determination of crystallization kinetic parameters of the selected composition.