The use of a liquid feedstock carrier in suspension plasma spray (SPS) permits injection of fine powders, providing the possibility of producing sprayed coatings that are both thin and dense and have fine microstructures. These characteristics make SPS an attractive process for depositing highly efficient electrodes and electrolytes for solid oxide fuel cell (SOFC) applications. In the present study, NiO-yttria stabilized zirconia (YSZ) anode and YSZ electrolyte half cells were successfully deposited on porous Hastelloy X substrates by SPS. The NiO-YSZ anode deposition process was optimized by design of experiment. The YSZ electrolyte spray process was examined by changing one parameter at a time. The results from the design-of-experiment trials indicate that the porosity of the as-deposited coatings increased with an increase of suspension feed rate while it decreased with an increase of total plasma gas flow rate and standoff distance. The deposition efficiency increased with an increase of total plasma gas flow rate, suspension feed rate and standoff distance. The microstructure examination by SEM shows that the NiO and YSZ phases were homogeneously distributed and that the YSZ phase had a lamellar structure. It was observed that the density of the YSZ electrolyte layer increased as input power of the plasma torch increased.

Metal-supported solid oxide fuel cells (SOFC) composed of a Ce 0.8 Sm 0.2 O 2-δ (SDC) electrolyte layer and Ni- Ce 0.8 Sm 0.2 O 2-δ (Ni-SDC) cermet anode were fabricated by suspension thermal spraying on Hastelloy X substrates. The cathode, a Sm 0.5 Sr 0.5 CoO 3 (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.