RSM-based optimisation for the processing of nanoparticulate SOFC anode material

The relationship between porosity and electronic conductivity of a Nickel-Yttria Stabilised Zirconia (Ni/YSZ) material was investigated using the Response Surface Methodology (RSM) technique. This advanced material is intended for use as the anode of a Solid Oxide Fuel Cell (SOFC). Tests were structured around a central composite design of experiments matrix. Ni/YSZ specimens were fabricated via a powder processing route, using precursor powders of nickel oxide (NiO) and YSZ, mixed with graphite that acts as a pore former. Porosity and conductivity measurements were performed on the material in the as-sintered stage as well as after the reduction process. Statistical analysis was performed using selected process parameters (sintering temperature and amount of graphite pore former) as input variables and porosity and conductivity as outputs. The contour plots obtained from the RSM technique were used to study the trend of porosity and conductivity. The results indicate that the porosity values decrease significantly beyond a certain sintering temperature, while the electronic conductivity increases significantly. A super-imposed porosity-conductivity contour plot was used to determine the optimal region for the desired porosity volume and conductivity value. Copyright © 2008 Inderscience Publishers.