Torsional shear strength of novel glass-ceramic composite sealants for solid oxide fuel cell stacks

To improve the mechanical strength of sealants for solid oxide fuel cell (SOFC) stacks, several fillers were proposed in this work as reinforcement for a glass‐ceramic sealant based on the system BaO‐CaO‐SiO2. The chosen reinforcement additives were metallic particles including nickel, a nickel‐chromium alloy and silver, as well as ceramics such as gadolinium‐doped ceria particles and yttrium‐stabilized zirconia particles or fibers. The glass‐ceramic sealant, with and without reinforcements, was used to join two parts made of stainless steel (Crofer22APU). A torsion test was used to measure the shear strength of the joined samples. The shear strength measurement by torsion gave reliable and reproducible results for all the joined samples. The lowest shear strength was found for the glass‐ceramic sealant without any reinforcement. The composite prepared of a combination of glass matrix and 20 wt.‐% Ni powder seems to be the best candidate sealant, able to fulfill all the requirements of a SOFC sealant. The samples made with this composite sealant presented the highest shear strength values as prepared and also after aging the sample in air atmosphere for 500 hours at 800°C.