The performance of NiO/NiFe2O4 coated pre-oxidized SUS 430 interconnect with different NiO thickness for solid oxide fuel cell

Abstract

Ni/NiFe2 coatings with different thickness of Ni were deposited on 50-h pre-oxidized SUS 430 steel by magnetron sputtering for solid oxide fuel cell (SOFC) interconnects application, which were subsequently exposed to 800 °C air for durations of up to 5040 h. Ni/NiFe2 coating was thermally converted to an oxide structure comprising inner NiO layer and outer NiFe2O4 spinel layer. The effects of different NiO diffusion barrier thickness on the oxidation behavior, electrical performance and long-term working stability of NiO/NiFe2O4 coated steel were investigated. The chromium vaporization from bare and coated steels was also evaluated at 800 °C in air-12 % H2O atmosphere. Results showed that scale delamination and the spike of area specific resistance (ASR) were achieved for the sample with thicker NiO layer after 2520 h thermal exposure. Moreover, NiO gradually migrated outward through the solid-state reaction between NiO and NiFe2O4 spinel and eventually aggregated near the outer surface. Breakaway oxidation of the bare steel occurred during the chromium vaporization test and undulating Fe oxide nodules were strewn on the steel surface. The chromium vaporization rate was effectively suppressed by the application of NiO/NiFe2O4 coating.