Evaluation of Inkjet Printed Protective Layer Coatings for SOFC Interconnects

Spinel based materials are regarded as effective coating materials in the protective layer application for the SOFC interconnects. In this work, aqueous based spinel inks were formulated for demand-on-drop inkjet printing process. Manganese Cobalt Oxide, MnCo2O4 (MCO) Manganese Cobalt Ferrite, MnCo1.8FeO4 (MCF) and MnCo1.6Fe0.2Cu0.2 (MCFC) were used as starting powder materials. Prepared inks were inkjet deposited over nitrided and non-nitrided K41 steel substrate and sintered at 800°C for 10 hours in ambient air. High-temperature ageing and Area Specific Resistance (ASR) tests were conducted for 1000 hours at 700°C in air with 3% humidity. There was no delamination or visible cracks observed on the inkjet printed layers. The recorded ASR values for all the samples were less than 0.1 Ohm.cm2 and nitrided K41 MCFC showed lower ASR value of 0.055 at Ohm.cm2 at 935 hours. Infiltrated K41 MCF showed the least amount of chromium presence of 0.55 atomic% at the cathode layer and was efficient in inhibiting the chromium diffusion across the protective layer. High-temperature oxidation test samples showed higher presence of chromium content on the protective layers due to their porous microstructure. Results of the study showed that further optimization of aqueous based suspension inks and their sintering conditions can improve the green density and hinder the chromium migration. Aqueous based inkjet deposition technique for protective layer applications showed promising results on par with other wet chemical deposition process and improvement of the performance will have significant impact on coating 3D interconnects structures.