GLASS AND GLASS-DERIVATIVE SEALS FOR USE IN ENERGY-EFFICIENT FUEL CELLS AND LAMPS

As the project approaches the end of the first year, the materials screening components of the work are ahead of schedule, while all other tasks are on schedule. For solid oxide fuel cells (SOFC), a series of 16 sealing glasses have been prepared and characterized. Traditional melting was used to prepare all of the glasses, and the sol-gel approach has been used to prepare some of the glasses as well as other compositions that might be viable because of the low processing temperatures afforded by the sol-gel method. The glass characterization included measurements of the viscosity and thermal expansion of the glasses, as well as the thermal expansion of the partly crystalline glass ceramics. In addition, the wetting and sintering behavior of all glasses has been measured, as well as the crystallization behavior. The time and temperature at which crystalline phases form from the glasses has been determined for all of the glasses. Each glass ceramic contains at least two crystalline phases, and most of the crystalline phases have been positively identified. Room temperature leak testing has been completed for all sealants, and experiments are in progress to determine the DC electrochemical degradation and degradation in wet hydrogen. The second component of the work, focused on seals for higher-temperature discharge lighting, has focused on determining the phase relations in the yttria--alumina--silica system at various silica levels. Again, traditional melting and sol-gel synthesis have been employed, and the sol-gel method was successful for preparing new phases that were discovered during the work. High temperature diffraction and annealing studies have clarified the phase relations for the samples studies, although additional work remains. Four new phases have been identified and synthesized in pure form, from which full structure solutions were obtained as well as the anisotropic thermal expansion for each phase. Functional testing of lamps are on on-going and will be analyzed during year 2 of the contract