Chapter 13 - Glasses and glass-ceramics as sealants in solid oxide fuel cell applications

Abstract

Currently used main energetic resources are based on fossil fuels, which produce a number of pollutants like SO2, NOx, CH4, chlorofluorocarbon, and CO2 in the atmosphere. Hence, it is incumbent on all countries to try to reduce the use of fossil fuels. As a consequence, the development of green energy by clean, efficient, and environmentally friendly materials is one of the major challenges. Due to high efficiency and low emission of pollutants, fuel cells are ideal candidates to solve this problem. Among various fuel cells, solid oxide fuel cells (SOFCs) are an emerging technology, which can not only reach very high energy conversion efficiencies (over 60%), but also offer great opportunities for carbon capture, due to theirseparate fuel and air flow streams. SOFCs have lower manufacturing costs and higher power densities compared to other fuel cells, but they require hermetic sealants to maintain a gas-tight state in between electrolyte and electrodes. One of the major challenges for the technology of intermediate temperature SOFCs is the development of suitable sealing materials to separate fuel and air. By lowering the operating temperature, a wider range of materials can be used that allow cheaper fabrication, particularly in relation to interconnects. For intermediate temperature SOFCs, sealants based on glasses or glass-ceramics are the most promising materials since their properties can be easily tailored by modifying glass compositions. The major advantages of these sealants are that they have a tunable coefficient of thermal expansion and high-potential long-term stability in thermal properties. This review discusses the properties of currently used glass and glass-ceramic sealant materials d and their development in high-temperature SOFC applications. This review also addresses the need for the adoption of different processing methods and various characterization techniques.