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Abstract: This paper reports the results of the thermal stability study of M–YSZ (M=Ni, Cu, Co, Cu–Co, Ni–Cu–Co) SOFC anode cermets materials at different heat treatment temperatures. The cermets were elaborated by atmospheric plasma spraying (APS) with optimized conditions and then submitted to heat treatments at 800 and 1000°C, respectively. Scanning electron microscopy and X-ray diffraction were used to characterize, respectively, the morphology and structure of obtained films, before and after thermal annealing. A correlation was made between the differential scanning calorimetry analysis results and those obtained by X-ray diffraction. Focusing, in this study, on YSZ matrix thermal stability, the obtained results were as follows: the monometallic cermets with the lowest amount of metal and the trimetallic one exhibited a good stability at 800°C, whereas at 1000°C, all considered cermets were unstable with a eutectoid decomposition of YSZ matrix. [Copyright &y& Elsevier]

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]

Abstract: A copper baseplate has been commonly adopted as a heat spreader material for power modules. However, the coefficient of thermal expansion (CTE) mismatch between copper and Si has always been a troublesome problem and the primary disadvantage of using a copper baseplate because the interface between the substrate and the heat spreader is one of the main failure sources of a power module. To solve this problem, the tailoring of a Cu–Mo composite material with high thermal conductivity and suitable thermal expansion coefficients was suggested by thermal spray process which makes it possible to easily fabricate components of functionally graded materials (FGMs) and allows the multiple steps of powder production, molding, degassing and consolidation to be reduced into a single processing step. By utilizing the vacuum plasma spraying technique, dense and well-distributed Cu–Mo metal matrix composite coatings without oxides and amorphous phase were obtained. Vertically grown intralamellar columnar structure, which is promising for increasing the heat transfer, was also observed in plasma sprayed Cu–Mo metal matrix composite coatings. Microhardness of Cu–Mo composite coatings follows a rule of mixture based on the volume fraction and fits nicely to a linear relation regardless of different measured temperatures. [Copyright &y& Elsevier]

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]

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: 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]

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]

Suspension plasma spraying (SPS) as a potential technique to prepare thermal barrier coatings (TBCs) has been attracting more and more attention. However, most reports on SPS were carried out in the atmosphere. Given the unique features of in-flight particles and plasma jets under low pressure, the resulting coatings are expected to be different from those under atmospheric pressure. In this article, yttria-stabilized zirconia (YSZ) thermal barrier coatings were prepared using suspension plasma spraying under different environmental pressures. The results show that as the environmental pressure decreased, the column-like structural coating turned into a vertical crack segmented structure, as well as a dramatic decrease in surface roughness. More nanoparticle agglomerates were formed in the coating under lower environmental pressures. The real porosity of the coating increased with a decrease in environmental pressure. [ABSTRACT FROM AUTHOR]

The effective modelling of configurable products must handle the complex problem of representation of the configurable products, learning new configurable products and analysis of their behaviour. However, currently in advanced CAD systems, there exists no systematic and effective method for designing configurations and integrating behavioural aspects and simulations. This paper proposes and develops a grammar-based design approach to support both the computer-aided design for configuration and computing in CAD systems. Two interrelated questions are taken into account: (1) What are the hypothesis, properties and features for product configuration? (2) How can the product based on configuration features be represented and how can the configuration representation method integrate the numerical computing in design? This approach, under the guide of the proposed formal modelling, is implemented in computers. A design case study illustrates the proposed approach. [ABSTRACT FROM AUTHOR]

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]

Abstract: Titanium dioxide is one of the most important photocatalysts that allows the environmental purification of various toxic organic compounds in water and removal of harmful air pollutants. In this paper, two techniques of plasma spraying – plasma spraying from an agglomerated nanopowder and liquid suspension plasma spraying – were used to produce thin deposits. The microstructure of coatings was characterized using scanning electron microscopy and X-ray diffraction. The photocatalytic properties of the coatings were evaluated by the decomposition test of nitrogen oxides and compared with the efficiency of the initial agglomerated nanopowder and that of the Degussa P25 powder. Noticeable different behaviours in the photocatalytic tests were observed for coatings performed either from conventional or liquid plasma spraying. The TiO2 deposits realized by spraying of the liquid suspension exhibited higher photocatalytic efficiency. It is found that the plasma spraying of a slurry is an effective method to retain the original anatase phase and prevent the increase of the crystallite size. This new method of modified spraying is proved to be a promising technique to elaborate photocatalytic coatings for the removal of nitrogen oxide pollutants. [Copyright &y& Elsevier]

Abstract: This paper deals with the study of the photocatalytic behaviours of TiO2 and TiO2–10wt.% Al coatings elaborated by high-velocity oxygen fuel (HVOF) spraying using spray-dried nanosized feedstock powders. In the HVOF flame, the powders were injected by two methods: internal injection, i.e. as in conventional HVOF process and external injection, i.e. outside the torch nozzle. Scanning electron microscopy and X-ray diffraction were employed to characterize the microstructure and the crystalline structure of the TiO2-based coatings. The photocatalytic activities were evaluated by the nitrogen oxides removal and compared with that of the initial powders. It was found that the amount of anatase in the coatings depends on the nature of the powder and also on the type of injection method. The TiO2 coatings, as well as, the TiO2–Al coatings elaborated using the external powder injection presented a better photocatalytic activity (the nitrogen oxides conversion rates were about 25–42% for NO and 14–18% for NO x ) than those obtained by the conventional HVOF process (<5%). Besides, TiO2 coatings containing aluminium particles had an enhanced photocatalytic activity than those of un-doped titania deposits. [Copyright &y& Elsevier]

Suspension plasma spraying (SPS) has attracted more and more attention in terms of the preparation of nanostructured ceramic coatings. However, due to the low mass of the nanopowder, it is challenging to prepare high-density coatings through SPS, and this largely limits its application in the areas such as electrolytes of solid oxides fuel cell (SOFC) and environmental barrier coatings. In this article, a novel suspension spraying technology – low-pressure suspension plasma spraying (LPSPS) – was used to prepare a high-density, nanostructured coating. The results revealed that the environment atmosphere (inert atmosphere versus oxidative atmosphere) played a critical role in the microstructure of the coating. The deposition mechanisms of the coatings in both atmospheres were proposed, and a high-density nanostructured yttria-stabilized zirconia (YSZ) coating was successfully prepared by atmosphere control, based on these deposition mechanisms. • A novel suspension spraying technique—low-pressure suspension plasma spraying was used to prepare dense nanostructured YSZ coating. • In the inert atmosphere, a number of carbons were produced in the plasma jet due to the ethanol pyrolysis, resulting in poor adhesion and mechanical properties of the coating • In the oxidative atmosphere, due to ethanol combustion, the plasma jet exhibited a better heating capacity for powders, resulting in improved quality of the coating. • A high-density YSZ coating was successfully prepared with a high-enthalpy plasma jet in the oxidative atmosphere [ABSTRACT FROM AUTHOR]