Reactive air brazing of the YSZ/AISI 310s couples using a novel Ag–Nb2O5 sealant.

A novel Ag–Nb 2 O 5 braze filler is developed and successfully tested as a sealant candidate for solid oxide cells. The resultant AgNbO 3 by the reaction between Ag and Nb 2 O 5 at high temperatures turns out to be the key to enable a desirable wetting of the YSZ by the braze filler. Typical interfacial microstructure of the YSZ/AISI 310s brazed joints are characterized by a scanning electron microscopy (SEM) and a transmission electron microscopy (TEM) with an energy dispersive spectroscopy (EDS). Effects of Nb 2 O 5 contents and joining parameters on the microstructural evolution and mechanical performance of the joints are investigated. Joints with a maximum average strength of 100–110 MPa are achieved when bonding at 1150 °C/30 min with 5 mol.% Ag–Nb 2 O 5. The long-term stability of the YSZ/Ag–Nb 2 O 5 /AISI 310s joints are evaluated in air for over 350 h at 800 °C and no cracks or cell degradation are found in the joints after the aging process, indicating that the new-developed Ag–Nb 2 O 5 is a promising candidate as the sealant for the SOFC stacks. [ABSTRACT FROM AUTHOR]