The effect of solids and dispersant loadings on the suspension viscosities and deposition rates of suspension plasma sprayed YSZ coatings

Suspension plasma spraying (SPS) is a promising modification of traditional plasma spraying techniques that uses small (≤ 2 μm) particles suspended in a liquid to fabricate coatings with fine microstructures and controlled porosity rapidly and without the need for post-deposition heat treatments. These qualities make SPS an interesting new technique to manufacture solid oxide fuel cell (SOFC) active layers. However, in order to be able to manufacture layers with good microstructures, the properties of the feedstock suspension must be optimized to enhance particle dispersion and improve feedability. This study uses a pressurized gas delivery system to feed aqueous YSZ suspensions containing an organic dispersant to a Northwest Mettech Axial III axial injection suspension plasma spray system. Three different dispersant types (polyacrylic acid (PAA), polyethylene imine (PEI) and 2-phosphonobutane-1,2,4-tricarboxylic acid (PBTCA)) were characterized and the effects of solid loadings, dispersant type, and dispersant concentration on suspension properties such as viscosity and feedability, and layer characteristics such as microstructure and deposited thickness were examined.