Suspension HVOF Spraying of Reduced Temperature Solid Oxide Fuel Cell Electrolytes

Metal-supported solid oxide fuel cells (SOFC) composed of a Ce_0.8Sm_0.2O_2-δ (SDC) electrolyte layer and Ni- Ce_0.8Sm_0.2O_2-δ (Ni-SDC) cermet anode were fabricated by suspension thermal spraying on Hastelloy X substrates. The cathode, a Sm_0.5Sr_0.5CoO₃ (SSCo)-SDC composite, was screen-printed and fired in-situ. The anode was produced by suspension plasma spraying (SPS) using an axial injection plasma torch. The SDC electrolyte was produced by high-velocity oxy-fuel (HVOF) spraying of liquid suspension feedstock, using propylene fuel (DJ- 2700). The emerging technology of HVOF suspension spraying was here explored to produce thin and low-porosity electrolytes in an effort to develop a cost-effective and scalable fabrication technique for high-performance, metal-supported SOFCs. In-flight particle temperature and velocity was measured for a number of different gun operating conditions and standoff distances and related to the resulting microstructures. At optimized conditions, this approach was found to limit material decomposition, enhance deposition efficiency and reduce defect density in the resulting coating, as compare to previous results reported with SPS. Produced button cells showed highly promising performance with a maximum power density (MPD) of 0.5 Wcm^-2 at 600°C and above 0.9 Wcm^-2 at 700°C, with humidified hydrogen as fuel and air as oxidant. The potential of this deposition technique to scale-up the substrate size to 50 X 50 mm was demonstrated.