Mechanochemical Approaches to Ceramic Ink Formulation for Digital Fabrication of Solid Oxide Fuel Cells

Abstract

Four different ink processing protocols were investigated to control the particle size distribution of lab scale batches of inkjet inks used for printing Solid Oxide Fuel Cell (SOFC) anodes. The inks were composed of a mixture of commercial Nickel Oxide (NiO) and Yttria-stabilized Zirconia (YSZ) powders dispersed in organic solvents. Protocols incorporating high energy wet and dry milling using a SPEX 8000 mixer mill were compared to traditional low energy milling/dispersion methods. Brunauer-Emmett-Teller (B.E.T.) surface area measurements were used in conjunction with scanning electron microscopy (S.E.M.) to determine the effects of the milling protocols on the dry powder particle sizes and morphologies. Dynamic light scattering (D.L.S.) was used to measure the particle size distributions of the inks. Low energy dispersion of the NiO and YSZ powders produced an ink with a number weighted particle size distribution peaked ∼ 300 nm and a significant tail of particles as large as 1 μm. Adding high energy dry milling or high energy slurry dispersion to the process removed most of the large particle size tail, but the particle size distribution remained peaked at 250 – 300 nm. By combining high energy dry powder milling with high energy slurry dispersion, the main peak in the particle size distribution shifted to 180 nm with minimal particles above 600 nm. These results indicate that the combination of high energy milling and dispersion enable lab scale production of nanoscale NiO/YSZ inks from commercial powders. The protocols developed in this work provide a first step towards the goal of controlling the microstructure of inkjet printed solid oxide fuel cell (SOFC) anodes through control of the ink particle size distribution.