resumo
Glasses and glass-ceramics (GCs), in particular alkaline-earth alumino silicate-based compositions, are becoming the most common sealing materials for gas-tight sealing applications in solid oxide fuel cells (SOFCs). The present review aims at reporting the systematic procedures put forward developing a novel concept of diopside-based bilayer GC seal, which contains a rigid GC and a self-healing (SH) GC. The concept behind the bilayer GCs is (i) a small gradient in the coefficient of thermal expansion (CTE) will lead to lower thermal expansion mismatch between the sealing layers and other SOFC components, thus providing enhanced mechanical reliability for the stack; and (ii) cracks produced due to minor thermal stresses in the rigid GC layer can be healed by the SH GC layer due to sufficient amorphous content. In general, at high temperature, highly crystallized glass behaves as a rigid glass. On the other hand, due to low viscosity behavior, partially crystallized glass provides a SH behavior. Various glasses in the field of diopside crystalline materials have been systematically designed by varying the chemical composition of glass to achieve desired combination of functional properties for the rigid and SH GC layers. The glass Sr-0.3 where Sr replaced 30 % of Ca was revealed as a highly reliable rigid GC seal for high-temperature electrochemical applications. On the other hand, SH features have been achieved in 30 % Sr-containing diopside-based glass with Gd2O3 for MgO + SiO2 substitution (denoted as Gd-0.3). These GCs exhibit similar thermal properties and excellent thermal stability along a period of 1000 h, while differing in their amorphous fractions, and revealed excellent thermal stability along a period of 1000 h. The bilayered GC synthesized from Sr-0.3 and Gd-0.3 showed good wetting and bonding ability to the SOFC metallic Crofer22APU components. The results revealed superior performance for the newly proposed bilayer GCs in comparison to single-layer sealants.
palavras-chave
OXIDE FUEL-CELLS; MOLECULAR-DYNAMICS SIMULATION; SYSTEMS RO-BAO-SIO2 R; SILICATE-GLASSES; LA2O3-NA2O-SIO2 GLASSES; ALUMINOBOROSILICATE GLASS; CRYSTALLIZATION KINETICS; ELECTRICAL BEHAVIOR; SINTERING BEHAVIOR; THERMAL-PROPERTIES
categoria
Electrochemistry
autores
Reddy, AA; Tulyaganov, DU; Kharton, VV; Ferreira, JMF
nossos autores
Allu Amarnath Reddy
Estudante de doutoramento
José Maria da Fonte Ferreira
Professor(a) Jubilado(a)
Vladislav Kharton
Investigador Principal Covidadoagradecimentos
This study was partially supported by the CICE CO, University of Aveiro, by the JECS-trust frontiers of research (201242-2), and FCT, Portugal (PTDC/CTM-CER/114209/2009). A. A. Reddy thanks FCT for the doctoral grant (SFRH/BD/89915/2012). V. V. Kharton acknowledges also the financial support of the Ministry of Education and Science of the Russian Federation (agreement 14.B25.31.0018) and the Russian Foundation for Basic Research (grant 13-03-12409). Important experimental contributions, partly reviewed in this work, and helpful discussions made by A. Goel and M. J. Pascual are gratefully acknowledged.