While the SOFC has great potential for stationary and mobile applications, it has a major flaw – the integrity of the seals within and between power-producing units. ‘The seal problem is the biggest problem for commercialization of solid oxide fuel cells,’ says Lu.
Composed of ceramic materials that can operate at 1000°C (1800°F), an SOFC uses such high temperatures to separate oxygen ions in the air. The ions pass through a crystal lattice and oxidize a fuel, usually a hydrocarbon. And when SOFCs are operated in reverse mode as solid oxide electrolyzer cells, pure hydrogen can be generated by splitting water.
In an SOFC stack, each module has air on one side and a fuel on the other. Many modules are stacked together to produce enough power for specific applications. Each module’s compartments must be sealed, and there must be seals between the modules in a stack so that air and fuel do not leak or mix, resulting in a loss of efficiency or internal combustion.
Lu’s new glass sealing material, based on SrO–La2O3–Al2O3–B2O3–SiO2, is free of barium oxide, calcium oxide, magnesia, and alkali oxides, and in addition contains almost imperceptibly low amounts of boron oxide. The research was originally reported last fall in the Journal of Applied Physics.
‘This is important, because the seals must be both mechanically and chemically compatible with the different oxide and metallic cell components as they are repeatedly cycled between room and operating temperatures,’ says Mike Miller, senior licensing manager with Virginia Tech Intellectual Properties.