Development of Intermediate Temperature (550 - 650oC) Metal Supported Solid Oxide Fuel Cells (SOFCs) Using Plasma Processes

Abstract

The primary problem in preparation of metal supported SOFCs, in almost all cases is reconciling the sintering characteristics of the metal support vis-a-vis the ceramic electrolyte/ anode functional layer, with which it is in contact. The sintering temperatures of dense ceramics are much higher than those of metal supports (Ferritic steels in this case), as also are differences in sintering atmosphere. As an alternative to using aids to lower the sintering temperature of ceramics (GDC and YSZ), thereby matching that of the substrate (which can lower electrical conductivity of the electrolyte), plasma spray deposition and plasma assisted co-sintering methods can be used effectively for multi-layered deposition, bonding and sintering. In this work, an entire cycle for fabricating a metal supported cell is discussed, using porous SS430L as anode substrate, NiO-GDC as anode functional layer, GDC as electrolyte and LSCF-GDC as cathodic layer. Other techniques such as tape casting for metallic substrates and Inkjet printing have also been incorporated into the manufacturing operations to engineer a metal supported SOFC cell. Key steps involve - Tape Casting of porous SS430L substrate layers, followed by vacuum sintering (1100 C)Inkjet printing/ Screen printing of anode (NiO + GDC) functional layers, followed by hot plasma surface treatment to induce sintering and bonding (‘Plasma Glazing’)Plasma Spray (powder) deposition of GDC electrolyte layer leading to bonding and sinteringInk-Jet printing of GDC colloidal suspension to give better finish to the ‘rough’ electrolyte surface, followed by ‘Plasma Glaze’Brush printing/ Screen printing of cathode (LSCF + GDC) layers on the electrolyte surface followed by ‘Plasma Glazing’ The above mentioned process is part of an ongoing Indo-UK program wherein NFTDC, with its partner, University Of Cambridge, UK, has taken a multi-disciplinary approach to developing a metal supported SOFC stack. This program includes - Materials synthesis and processing (GDC, LSCF), Stack design and Interconnect fabrication, Cell-Stack assembly, along with Electrochemical and microstructural characterization, and finally, process design of the overall system that can operate on commercial Natural Gas or Higher hydrocarbon fuels.