NiMn2O4 spinel as an alternative coating material for metallic interconnects of intermediate temperature solid oxide fuel cells

In an effort to improve the performance of SUS 430 alloy as a metallic interconnect material, a low cost and Cr-free spinel coating of NiMn2O4 is prepared on SUS 430 alloy substrate by the sol–gel method and evaluated in terms of the microstructure, oxidation resistance and electrical conductivity. A oxide scale of 3–4 μm thick is formed during cyclic oxidation at 750 °C in air for 1000 h, consisting of an inner layer of doped Cr2O3 and an outer layer of doped NiMn2O4 and Mn2O3; and the growth of Cr2O3 and formation of MnCr2O4 are depressed. The oxidation kinetics obeys the parabolic law with a rate constant as low as 4.59 × 10−15 g2 cm−4 s−1. The area specific resistance at temperatures between 600 and 800 °C is in the range of 6 and 17 mΩ cm2. The above results indicate that NiMn2O4 is a promising coating material for metallic interconnects of the intermediate temperature solid oxide fuel cells.

► A preferred microstructure of the oxide scale formed during oxidation at 750 °C in air for up to 1000 h. No Cr-containing oxide is directly exposed to air, which will depress the Cr evaporation.
► An improved oxidation rate 5.0 × 10−15 g2 cm−4 s−1 of the coated SUS 430 alloy.
► An reduced electrical resistance of the coated SUS 430 alloy oxidized at 750 °C in air for 1000 h. In the temperature range of 600–800 °C, the area specific resistance is between 6 and 17 mΩ cm2.