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Polished cross sections of plasma-sprayed yttria-stabilized zirconia coatings deposited using different process parameters were prepared with both hot- and vacuum-mounting techniques and investigated by image analysis. It was found that polishing-induced pull-outs were evidently present on the hot-mounted cross sections, and that the perimeter of these pull-outs could be described statistically by means of fractal analysis. In this work, values of the corresponding fractal dimension range from 1.45-1.54; they increase linearly while increasing fracture toughness, and decrease with the increase in porosity of the coatings. Thus, this fractal dimension may be regarded as a measure of the fracture toughness of the coatings, but only for hot-mounted samples. [ABSTRACT FROM AUTHOR]

Abstract: The apatite-type lanthanum silicate films were successfully synthesized by modified atmosphere plasma spraying using lanthanum oxide and silicon oxide mixed powders and precalcined hypereutectic powders in the size range 1–3μm and 5–8μm, respectively, as starting feedstock materials. The films differed not only in microstructural scale, but also in the characteristic of the degree of film densification. A detail describing the evolution of microstructure has been discussed. A considerable improvement in densification of the La10(SiO4)6O3 electrolyte films has been observed. [Copyright &y& Elsevier]

Abstract: This paper deals with the elaboration of titanium dioxide coatings, designed for photocatalytic applications, obtained by a non-conventional method of deposition, suspension plasma spraying (SPS), an alternative of the atmospheric plasma spraying (APS) in which the material feedstock is a suspension of the material powder to be sprayed. TiO2 P25 powder (Degussa AG) mechanically dispersed in distilled water and/or ethanol was injected in argon–hydrogen and argon–hydrogen–helium plasma under atmospheric conditions. Scanning electron microscopy and X-ray diffraction were performed to study the morphology and the crystalline phases of the titania coatings. Surface features were investigated by Fourier transform infrared (FT-IR) and X-ray photoelectron spectroscopy (XPS). Photocatalytic efficiency of the elaborated samples was tested in an environmental test chamber set-up and evaluated from the conversion rate of nitrogen oxides. The results showed that the coating obtained from the injection of an alcoholic suspension contained 23% of anatase ratio and ensured a very low photocatalytic decomposition of nitrogen oxides. In contrast, the injection of an aqueous suspension into the plasma permitted to obtain deposits where the anatase phase and the crystallites size were preserved. Also, a conversion rate of the pollutants of about 40%, slightly better compared to that of the initial P25 powder (around 32%) was noticed. This slightly higher efficiency was correlated with a cleaning of the particles surfaces when crossing the plasma and a higher hydroxylation of the coating surface. [Copyright &y& Elsevier]

An artificial neural network (ANN) was built to analyze the decrease of nitrogen oxides relative to TiO2 powder photocatalytic efficiency. Experimental sets were considered to train and test ANN where it was possible to identify an optimized structure representing the correlations between experimental variables and NO and NOx efficiencies. Predicted results permitted to point out the role of exposed surface and powder mass. [Copyright &y& Elsevier]