Ceramics

Biography

Biography: Allu Amarnath Reddy

Abstract

Glass and glass-ceramic (GC), in particular alkaline-earth alumino silicate based glasses and GCs, are becoming the most common sealing materials for gas-tight sealing applications in SOFCs. Besides the development of new glass-based materials, new additional concepts are required to overcome the challenges being faced by the currently existing sealant technology.In this pursuit, various glasses and GCs in the field of diopside crystalline materials have been synthesized and characterized by a wide array of techniques. All the glasses were prepared by melt-quenching technique while GCs were produced by sintering of glass powder compacts at the temperature ranges from 800900 ºC for 11000 h. Furthermore, the influence of various ionic substitutions, especially SrO for CaO, and Ln2O3 (Ln=La, Nd, Gd, and Yb), for MgO + SiO2 in Al-containing diopside on the structure, sintering and crystallization behaviour of glasses and properties of resultant GCs has been investigated, in relevance with final application as sealants in SOFC. From the results obtained in the study of diopside-based glasses, a bi-layered concept of GC sealant is proposed to overcome the challenges being faced by SOFCs.Bi-layer GC contains a rigid and a self-healing (SH)GC layer. The concept behind the Bi-layer GC is : (i) a small gradient in the CTE will lead to lower thermal expansion mismatch between the sealing layers and the other SOFC components, thus provide enhanced mechanical reliability for the stack; (ii) cracks produced due to minor thermal stresses in the rigid GC layer can be healed by the SH-GC due to its sufficient amorphous content. Obtained experimental results from chemical, thermal, mechanical and electrical studies confirm the good suitability of the investigated bi-layered sealant system for SOFC applications.