In this investigation, particle image velocimetry (PIV) diagnostics were employed to analyze the spray produced by a two-fluid atomizer as used in suspension plasma spraying (SPS). This led to a change in the design of the atomizing nozzle in order to achieve a high-speed spray with narrow distributions in droplet size. The resultant spray was characterized and the diagnostic was adapted accordingly. Various suspensions of YSZ powders were then injected into the plasma under different conditions and particle velocities were determined and correlated with the coating morphologies obtained.

In order to achieve SOFC at reduced costs, atmospheric plasma spraying (APS) could be an attractive technique. However, it is difficult to elaborate plasma sprayed coatings with the appropriate porosity for the electrodes and full density for the electrolyte. The spray process has been adapted by providing a suspension as feedstock material. SPS shows important advantages over APS, since it is now possible to spray finer powders to obtain either a thin (10 µm) dense layer as electrolyte or thick and finely structured porous layers for the electrodes. Nevertheless some questions still remain before considering manufacturing SOFC by SPS. The major one is to understand the influence of the suspension and the injection parameters on the drops formation and transformation in plasma before impinging upon the substrate as well as of the suspension characteristics (formulation, particle size and amount, viscosity, surface tension,...). To answer these questions, suspensions based on nickel oxide (NiO) and YSZ (yttria stabilized particles) have been prepared and functional layers have been produced by SPS. This work is compared with previous studies of YSZ sprayed suspensions.

In order to achieve Solid Oxide Fuel Cells (SOFC) with reduced costs, the atmospheric plasma spray process (APS) could be an attractive technique. However, it is difficult to produce plasma sprayed coatings with the appropriate porosity for the electrodes and full density for the electrolyte. The spray process has been adapted by providing a suspension or a powder as feedstock material combined with optimized spray conditions to manufacture SOFC layers with required compositions, microstructures and properties. Suspensions or powders were injected in a plasma jet originating from a conventional torch (F4) implementing external devices. By using optimized suspensions of nickel oxide (NiO) and yttria stabilized zirconia (YSZ) in ethanol, porous anodes have been produced with thicknesses around 50 µm. By the same way aqueous suspensions of yttria stabilized zirconia (YSZ) powders have been prepared to achieve a fine layer as electrolyte to produce the first half cells and the porous cathode layers based on lanthanum strontium manganite (La 0.8 Sr 0.2 MnO 3 or LSM) have been manufactured by conventional atmospheric plasma spraying of powders.