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Abstract: To improve the internal reforming reactions at SOFC anode, alternative (Ni, Cu, Co) –YSZ and Cu-Co-YSZ anode cermets materials are coated by atmospheric plasma spraying (APS). The spray parameters including carrying gas flow rate, spraying distance, argon flow rate and hydrogen flow rate were investigated by an orthogonal experiment to fabricate gas-permeable anode cermets coatings. Scanning electron microscopy and X-ray diffraction are used to characterise the morphology and structure of coated films respectively. The porosity was deduced by the statistical image analysis. By proper selection of the spray parameters to decrease the particles velocity and temperature, the sprayed coatings monometallic and bimetallic ones show that the cross porosity is dependent of metal weight ratio. In fact, when the metal percentage increases, the porosity decreases. Monometallic Ni-YSZ, Cu-YSZ and Co-YSZ cermets with a weight ratio of (3:2) appear to be less porous than those with (1:1) and (2:3) ones respectively, to reach a maximum porosity of 21.57% for Co-YSZ cermet of (2:3) weight ratio. Cu-Co-YSZ bimetallic cermet coating with weight ratio of (0.5:1:2.5) is more porous than those with (1:2:3) and (2:1:2) weight ratios respectively. Its porosity is about 19.15% which is closed to that of Ni-YSZ (2:3) coating. The X-ray diffraction results showed that the metal content in the cermets have a negligible influence on the crystalline phase structure. Such bimetallic materials anode are very interesting because Co diffuses in Cu lattice offering thus, best electronic conductivity, thermal stability and an avoided carbon formation, by replacing Ni with an electron conductor such as Cu that does not catalyze carbon formation. [Copyright &y& Elsevier]

Titanium dioxide is a very useful photocatalyst for the decomposition and diminution of environmental water and air pollutants. In such applications, it can be used as slurry or as immobilized coating obtained by different deposition methods. The studies performed in the last years showed that thermal spraying could be employed to elaborate TiO2 coatings with high performance for the decomposition of organic compounds. This manuscript presents a comparative study on the microstructure and photocatalytic performance of titania coatings obtained by different thermal spray techniques: atmospheric plasma spraying (APS), suspension plasma spraying (SPS), and high-velocity oxygen fuel spray process (HVOF). Different titania powders and suspensions were used to study the influence of the feedstockmaterials on the coating characteristics. The deposits weremainly characterised by SEM and X-ray diffraction. The photocatalytic performance was evaluated from the removal of nitrogen oxides. The experimental results showed that a drastic reduction of the pollutant concentration was obtained in presence of coatings elaborated by suspension plasma spraying. TiO2 coatings resulting from the spraying of agglomerated powder presentd less efficiency. That was mainly explained by the significant phase transformation from anatase to rutile that occurred in the enthalpic source during the spray processes. [ABSTRACT FROM AUTHOR]

Abstract: TiO2 and TiO2–Al composite coatings were prepared by plasma spraying using a reconstituted nanosized feedstock via a spray drying method. Effects of various spray conditions on the microstructure, porosity, microhardness and wear resistance related to the mechanical performance of coatings were evaluated. The coatings sprayed using relatively low plasma power were composed of two distinct microstructures of well defined lamellar structure, similar to microstructure of conventional plasma sprayed coatings generated by fully melted particles, and embedded nano or sub-micron particles generated by partial/non-molten particles of feedstock materials. The fraction of partial/non-molten particles in coating layers was increased by Al additive. Such a characteristic of blended microstructure of coatings was clearly confirmed from a bimodal distribution of microhardness described by Weibull plots. The optimized addition of Al into TiO2 increased the spraying efficiency, and also, improved mechanical properties such as microhardness and wear resistance. [Copyright &y& Elsevier]

Abstract: Very Low-Pressure Plasma Spray (VLPPS under 1mbar) has been developed and used for deposition of copper powder (10–63μm) coating on stainless steel substrate. In order to improve the understanding of this technique and to study the volatilization of the injected powder in supersonic plasma, optical emission spectroscopy study has been carried out. Preliminary results of the properties and the structure of VLPPS copper coating are presented. It is shown that the plasma expansion with decreasing chamber pressure increases the volatilization of particles and allows to obtain a very dense coating with crystalline structures and avoids oxygen, due to the preheating of the substrate with plasma (length about 1.50m). [Copyright &y& Elsevier]

Abstract: In thermal spraying, temperature, size and velocity of particles before they impact on the substrate are among the main characteristics influencing the microstructure of the resulting coating. Individual in-flight particle characteristics can be measured by using various optical techniques developed in the laboratory or available on the market. Some of these techniques aim to estimate the individual particle thermal radiation by forming an image of the particles when they pass in front of a collecting lens. In thermal spraying, and more specifically in plasma spraying, measuring the thermal radiation of individual sprayed particles can be a challenging task because of the intense radiation coming from the plasma. The aim of this work is to quantify the error made in estimating particle thermal radiation from measurement of visible and near-infrared radiation coming from individual particles. To achieve this goal, two kinds of measurements were made. First, optical radiation emitted, or reflected, by a jet of sprayed particles is analyzed by an optical emission spectrometer. Then, after triggering by laser light scattering on individual cold particles, the near-infrared radiation collected from those particles is measured as it is usually done by two-color pyrometry on hot sprayed particles. Analysis of these measurements allows us to estimate the accuracy of thermal radiation measurement and then the error made on particle surface temperature in thermal spraying diagnostic. [Copyright &y& Elsevier]