Reactive-Element-Free, Silver-Based Brazes for SOFC Applications

Reactive air Ag-CuO brazes are the most widely used SOFC brazes today. Unfortunately, the high similar to 45 degrees wetting angle of the conventional Ag-4 wt.% Cu braze often leads to braze joint manufacturing defects. Furthermore, the reduction of CuO during dual atmosphere (H-2/O-2) SOFC operation results in pores that: i) mechanically weaken the braze interfaces and ii) provide a short-circuit path for H-2 invasion into the center of the braze (thereby hastening the development of gaseous water pockets formed when oxygen and hydrogen meet within the braze). The present work shows for the first time that porous nickel layers allow high-quality yttria stabilized zirconia -stainless steel braze joints to be produced using reactive-element-free, silver-based brazes. It is expected that the elimination of porosity enabled by this new brazing method will increase SOFC braze joint reliability and lifetime.