Fabrication of finely structured silicon-supported SOFC with anode deposited by multi-phase plasma spraying

The mechanically mixed NiO/YSZ powder was usually used as the anode material of atmospheric plasma sprayed (APS) solid oxide fuel cells (SOFC). Big particles and the non-uniform distribution of the pores were observed in the resultant anode layer. To overcome the limitations, a method of fabricating anode layer by multi-phase plasma spraying (MPS) was proposed in this paper. The NiO and YSZ powders were delivered into plasma jet by a separate injection, where nitrogen carrier was employed to feed micrometer-sized NiO powder and liquid carrier was to feed submicrometer-sized YSZ powder. Suspension plasma spraying (SPS) was applied to fabricate dense electrolyte layer. The microstructure and composition of coatings were characterized by SEM and EDS. The results showed that finely structured anode layer with small particle size (d ∼ 2 μm) was achieved by the MPS method. The MPS anode layer was porous with the porosity of 32.1% while the APS anode layer was 22.6%. Three kinds of elements (Ni, Y, Zr) were observed in the MPS anode layer and the NiO content was calculated to be 49.6 wt%. In the SPS process, the suspension flow rate was matched to the plasma gas flow rate to obtain proper injection condition.

► To overcome the limitations of coarse microstructure and the non-uniform distribution of the pores in traditional plasma sprayed anode, a method of fabricating anode layer by multi-phase plasma spraying (MPS) was proposed in this paper. The NiO and YSZ powders were delivered into plasma jet by a separate injection, where N2 carrier was employed to feed micrometer-sized NiO powder and liquid carrier to feed submicrometer-sized YSZ powder. Finely structured anode layer with small particle size (d ∼ 2 μm) was achieved by the MPS method. The MPS anode layer was porous with the porosity of 32.1%. The content of Ni element in the anode was 50.89 wt% according to XRF.
► The spraying distance and liquid injection conditions were studied to fabricate dense electrolyte. The porosity of the electrolyte layers are 3.4%, 8.7% and 12.7% at the spraying distance of 50 mm, 60 mm and 70 mm, respectively. The selection of RPS was used to evaluate injection conditions. To ensure most of the particles inject into the hot zone of plasma jet, the suspension flow rate was matched to the plasma gas flow rate.
► The silicon substrate was studied for plasma sprayed SOFCs in the paper. The MPS anode/substrate adhesion is close to APS anode/substrate. Three-dimensional PEN with air channel can be micro patterned using etching mask at the opposite side of the silicon substrate.