Infrared images are used to characterize the atmospheric plasma and the influence of the liquid injection. In the infrared spectral range of low energies of the rotational vibrational transitions can be captured, which are emitted by hot liquid vapors. In addition, the combustion of organic liquids like ethanol and pentanol can be seen directly with an increase of the emitted radiation. The examination of the spray clouds suggests a correlation between Ohnesorge number and the spray angle. Lower Ohnesorge numbers lead to more focused vapor beams.

Liquid injection plasma spraying is of growing interest for thermal spray applications like thermal barrier coatings and solid oxide fuel cells, since finely structured coatings offer improved properties over conventionally spray ones, for example lower thermal diffusivity and higher catalytic activity. One challenge is the optimization and understanding of the injection process. With a new high speed shadowgraphy setup, the injection and atomization of individual drops was observed and described in detail in this work which is, to our best knowledge, not reported before. A drop atomization cone model is derived from observations. A new modelling approach is developed which allows the prediction of the drop atomization cones by analytical calculations. The simulations are compared to measurements and deviations are explained by neglected effects which will be included in further developments of this model.

La 1-x Sr x Co 0.2 Fe 0.8 O 3-δ deposits, of different stoichiometry, were fabricated for SOFC oxygen electrode using atmospheric plasma spraying (APS) with TriplexPro gun. The spraying conditions were developed by correlating, plasma jet characteristics (enthalpy and velocity), in-flight particle properties (temperature and velocity) and deposit quality (phase composition, porosity, coefficient of thermal expansion, electrochemical testing). The optimal cathode deposits exhibited a porosity of about 20 vol.%. The CTE in air flow at 800 °C was, however, 15.6 x 10 -6 K -1 and it was independent of the processing conditions. Electrochemical tests for cathodes were conducted on SOFCs that were produced following metal supported design and had YSZ as electrolyte and NiO+YSZ as anode. At 800 °C, power densities of above 640 mW/cm 2 at 0.7 V were recorded with H 2 /air for cell having La 0.60 Sr 0.40 Co 0.2 Fe 0.8 O 3-δ as cathode. Cells consisting of La 0.58 Sr 0.4 Co 0.2 Fe 0.8 O 3-δ and La 0.78 Sr 0.2 Co 0.2 Fe 0.8 O 3-δ had 479 and 496 mW/cm 2 under similar conditions. Using equivalent circuit diagrams the contribution of different polarizations on the cell performance were separated and cathodes were compared. La 0.60 Sr 0.40 Co 0.2 Fe 0.8 O 3-δ was found to have the best electrochemical performance followed by La 0.58 Sr 0.40 Co 0.2 Fe 0.8 O 3-δ and La 0.78 Sr 0.20 Co 0.2 Fe 0.8 O 3-δ .

Impact of liquid injection on atmospheric plasma has been measured by an enthalpy probe and visualized by shadowgraphy. Liquid was injected by two nozzles. A solid stream nozzle with 0.3 mm diameter and an atomizing nozzle with a spray angle of 30°. For constant liquid flow rate and varied plasma current an optimal injection parameter has been obtained. Influence of different flow rates on plasma characteristics has been examined. Full profiles along each axis show differences for different injection techniques in enthalpy, temperature, velocity and composition.