Aerosol sprayed Mn_1.5Co_1.5O₄ protective coatings for metallic interconnect of solid oxide fuel cells

A stable suspension has been obtained by disbursing Mn_1.5Co_1.5O₄ (MCO) particles (100–300 nm in diameter) in ethanol using a ball milling process. The suspension is used for deposition of a uniform MCO coating (5–8 μm thick) on a steel (T441) substrate preheated to 200 °C by aerosol spraying. It is found that the grain size of spinel crystals in the MCO coatings ranges from 100 nm to 1 μm, and remains uniform and stable when exposed to air at 800 °C for 1000 h. However, a Cr-rich oxide scale of approximately 0.75 μm thick appears between the MCO coating and the T441 substrate during the exposure. In contrast, a bare T441 sample (without the MCO coating) is oxidized significantly more under the same exposure, forming an oxide scale of 4 μm thick. The result indicates that the spinel coating had effectively improved the oxidation resistance of T441 by inhibiting the transport of Cr. Besides, the results also suggest that aerosol spraying is a simple and cost-effective method for deposition of thin and dense protective coating.