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In this work, we investigate the effect of coal power plant exhaust gas on amino-modified mesoporous ceramic membranes. The testing of ceramic membranes in the flue gas of coal-fired power plants represents a new approach, as testing under simulated flue gas conditions has already been undertaken, but not yet during direct exposure to exhaust gas. Flue gas exposure trials were carried out at a lignite-fueled power plant and a hard-coal-fueled power plant. Most experiments were conducted using a test rig designed to bring planar membrane samples in direct contact with unconditioned flue gas in the exhaust gas channel. Another test rig was designed to test membrane modules with pre-treated flue gas. The tested membranes had an asymmetrical structure consisting of a macroporous α-Al 2 O 3 support coated with a mesoporous γ-Al 2 O 3 or 8YSZ interlayer. The microporous functional top layer was made of amino-functionalized silica. The tests revealed different degradation mechanisms such as gypsum/fly ash deposition on the membrane surface, pore blocking by water condensation, chemical reactions and phase transformation. A detailed analysis was carried out to evaluate their impact on the membrane in order to assess membrane stability under real conditions. The suitability of these membranes for this application is critically discussed and an improved mode of membrane operation is proposed. [ABSTRACT FROM AUTHOR]

Abstract: Nonstoichiometric yittrium-substituted SrTiO3 samples with a nominal composition of Sr x Y0.07TiO3± δ (x =0.87–1.01) and Sr0.895Y0.07Ti x O3 − δ (x =1.00–1.20) were prepared and investigated. Phase impurities were found in samples with too high A-site or B-site deficiency. The electrical properties of the samples sintered in reducting atmosphere at different temperatures were analyzed with a view to their potential use as anode materials for solid oxide fuel cells (SOFCs). The redox properties of selected samples were investigated in detail. Samples with small A-site deficiency were considered to be the best candidates for SOFC anode materials. [Copyright &y& Elsevier]

Abstract: The interdependence between plasma spray process parameters and porosity of YSZ coating microstructures was investigated with simultaneous consideration of the deposition efficiency. Based on a factorial experimental plan, the argon plasma gas flow, the current, the interaction of argon flow and current, and the spray distance for the Triplex II plasma gun were found to yield the main contributions to porosity as well as to deposition efficiency. Each of these three process parameters has a significant individual effect on the in-flight particle velocities and temperatures. The contribution to the effects on porosity arises almost exclusively from the particle temperature. Regarding the deposition efficiency, the larger contribution originates from the particle velocity. To achieve a targeted high porosity at reasonable deposition efficiency a simple linear regression model was applied yielding an argon flow of 50slpm and a current of 470A at a spray distance of 200mm as the optimum parameter set. The average particle temperature estimated for this optimum is just above the melting temperature. At this setting, a porosity of 17.7% and a deposition efficiency of 32.5% may be expected. At a greater spray distance and lower power density (lower current and/or higher argon plasma gas flow) the deposition efficiency was observed to drop considerably. The cooling of the particles here becomes critical, i.e. the particles are only partly molten. This was verified by an analysis of the density distributions of measured in-flight particle temperatures. [Copyright &y& Elsevier]

Abstract: Single phase (La,Sr)(Al,Mn)O3 perovskites were synthesized and their electrical conductivity was studied as a function of temperature and oxygen partial pressure. The electrical conductivity was found to increase with Mn content, temperature and oxygen partial pressure, thus (La, Sr)(Al, Mn)O3 may be regarded as a diluted system of (La,Sr)MnO3. The highest electrical conductivity at 810 °C in air and humidified Ar/4% H2 was observed for (La0.8Sr0.2)0.94Al0.5Mn0.5O3 and reached 12 and 2.7 S/cm, respectively. [Copyright &y& Elsevier]

Abradable coatings have been used in low- and high-pressure sections of jet engine compressors for more than 40 years. Today, they are also used in the high-pressure turbine of jet engines and are gaining more interest for applications in industrial gas turbines. They minimise the clearance between the rotating blade tips and the stationary liners. Aside from being abradable, the coatings have to be mechanically stable and withstand high thermo-mechanical loadings. A typical material used in engines today is yttria-stabilised zirconia (YSZ). This material advantageously combines a suitable thermal conductivity with a high thermal expansion coefficient, but shows a temperature capability limited to 1200°C in long-term applications. Typical abradable coating thicknesses are above 1mm. With increasing coating thickness and limited cooling efficiency leading to high surface temperatures, there is a risk of premature failure. As a result, new ceramic materials have been developed with better high-temperature capability. The present work investigates an atmospheric plasma sprayed ceramic double-layer coating system composed of 7YSZ as an intermediate layer and magnesia alumina spinel as a top layer. This double-layer system was sprayed onto disc-shaped Inconel 738 superalloy substrates, which were coated with a vacuum plasma sprayed MCrAlY bondcoat. The lifetime of the coating system was assessed via thermal gradient cycling testing with surface temperatures above 1400°C. During cycling, the samples showed a typical failure mechanism with exfoliation of thin coating lamellae starting from the coating surface. This failure mechanism was not observed in thermal barrier or abradable coatings in the past. The failure mechanism was analysed and mismatch stress calculations were carried out. [ABSTRACT FROM AUTHOR]

Abstract: Perovskite Ba(Mg1/3Ta2/3)O3, BMT has promising bulk properties (thermal conductivity ~2W/m-K and coefficient of thermal expansion ~11×10−6/K at 1473K) for thermal barrier coating (TBC) applications at high temperature. However, during atmospheric plasma spraying (APS), such material was found to lose constituents due to the differences of vapor pressures resulting to non-stoichiometric composition of deposited coatings. To investigate the extent of phase decomposition at spray distance and varying electric arc current, different feedstock powders were plasma sprayed into water and collected for chemical, microstructural and phase analyses. When the electric arc current was decreased from 500A to 300A, the decomposition of the powders was reduced and the microstructure of the deposited coatings was improved. The thermal cycling lifetime of the deposited coatings at ~1250°C surface temperature is also higher. [Copyright &y& Elsevier]

Abstract: The application of a thin film electrolyte layer with a thickness in the micrometer range could greatly improve current solid oxide fuel cells (SOFCs) in terms of operating temperature and power output. Since the achievable minimal layer thickness with conventional powder coating methods is limited to ∼5μm, a variety of thin film methods have been studied, but results on regular large-scale anode substrates are still lacking in the literature. In this paper, a wet coating process is presented for fabricating gas-tight 1–2μm thick 8YSZ electrolyte layers on a regular NiO/8YSZ substrate, with a rough surface, a high porosity and a large pore size. These layers were deposited in a similar way as conventional suspension based layers, but the essential difference includes the use of coating liquids (nano-dispersion, sol) with a considerably smaller particle size (85nm, 60nm, 35nm, 6nm). Successful deposition of such layers was accomplished by means of an innovative coating process, which involves the preparation of a hybrid polyvinyl alcohol/8YSZ membrane by dip-coating or spin-coating and subsequently burning out the polymer part at 500°C. Results from He leak tests confirmed that the sintered layers posses a very low number of defects and with values in the range 10−4–10−6 (hPadm3)/(scm2) the gas-tightness of the thin film layers is satisfactory for fuel cell operation. Moreover, preliminary results have also indicated a potential reduction of the sintering temperature from 1400°C to the range 1200–1300°C, using the presented coating process. [Copyright &y& Elsevier]

Abstract: Donor-substituted SrTiO3 ceramic materials were investigated as the anodes of solid oxide fuel cells (SOFCs). Sr0.89Y0.07TiO3−δ (SYT) samples with good electrical conductivity and redox stability were prepared. The thermal and chemical expansions of SYT are both compatible with YSZ electrolyte. Half cells consisting of a flat anode substrate and an electrolyte layer with outer dimensions of 5cm×5cm were fabricated, Ni particles were infiltrated on the pore walls within the ceramic anode framework, and the redox stability of the half cell was tested by He leakage tests after redox cycling. Ti diffusion but no Sr migration was found between the anode and electrolyte layers. Sr0.895Y0.07Ti x O3±δ (x =1.00–1.20)–YSZ composites with a volume ratio 2:1 were prepared to investigate the influences of this interdiffusion between YSZ and SYT materials. The results indicate that the conductivity of SYT decreases because of the Ti diffusion, and a small amount of Ti excess can solve this problem. [Copyright &y& Elsevier]

Abstract: Highly porous TiO2 coatings have been produced by suspension plasma spraying on ITO coated glass substrates. The deposition process could be optimized so that fine/nano grained highly porous coatings were obtained. Mean crystallite sizes well below 50 nm could be achieved in the coatings for the anatase phase. Special emphasis was on the establishment of a high volume fraction of the desired anatase phase. The best coatings showed values of about 90% of anatase phase. With these coatings photovoltaic cells could be produced. Different levels of layer thickness and porosity as well as contents of anatase phase have been investigated. In the paper details on the microstructure of the cells as well as the photovoltaic performance will be given. [Copyright &y& Elsevier]

Abstract: Perovskites resulting from discrete changes in composition within the quasi-ternary system La0.8Sr0.2MnO3−δ –La0.8Sr0.2CuO2.4+δ –La0.8Sr0.2FeO3−δ were investigated under constant experimental conditions with the objective of obtaining an overview of the variation of the properties relevant for possible future applications. Nineteen nominal perovskite compositions within this system were systematically selected and synthesized under identical conditions by the Pechini method. The experimental data obtained on quantitative chemical analysis, powder X-ray diffraction, electrical conductivity and thermal expansion are presented collectively for the first time to facilitate comparisons. The formation and distribution of the different crystallographic phases at 950°C within this quasi-ternary system are shown. The DC electrical conductivity is strongly influenced by the Cu content and increases up to 276Scm−1 for La0.8Sr0.2CuO2.4+δ . The thermal expansion is dominated by the Cu/Mn ratio and is almost independent of the Fe content. [Copyright &y& Elsevier]

Abstract: A novel processing method to produce a carbon-fibre-reinforced silicon carbide (C/SiC) is presented and the mechanical properties are evaluated. The low-cost process yields a reaction bonded silicon carbide matrix but avoids efficiently reactive damage of the carbon fibres. Thus, the C/SiC-material shows a fibre-dominated behaviour due to high fibre strength and matrix porosity. The characteristics and mechanical properties of this C/SiC are highlighted. The discussion deals with the particular mechanical characteristics of porous-matrix materials relating to similar materials investigated hitherto. [Copyright &y& Elsevier]

Abstract: A carbon-fibre-reinforced carbon (C/C) composite filled with silicon carbide (SiC) particles was produced, using the winding technique. A porous matrix consisting of glassy carbon, SiC particles and small pores in homogeneous distribution was produced, ensuring a damage-tolerant fracture behaviour. Neither fibre coatings nor further infiltration steps were necessary for the preparation of the composite, which makes this a low-cost process making no limitations on wall thickness. The microstructure and homogeneity of the material is shown using micrographs, mercury porosimetry and BET measurements. Bending tests, as well as single-edge notch beam (SENB) tests point to high values for the bending strength and formal fracture toughness. A damage-tolerant fracture behaviour is demonstrated by the load–displacement curves and fracture surfaces. [Copyright &y& Elsevier]

The concept of anode-supported planar solid oxide fuel cells (SOFCs) involves different fabrication procedures and several sintering steps. This contribution is an attempt towards minimizing the number of sintering steps. By adopting an improved technique a pre-firing step was eliminated. Cells obtained following this co-firing technique showed relatively higher power density (∼1 A cm-2 at 0.7 V) at an operating temperature of 800 °C compared to the cells prepared by the conventional technique. In the present investigation, cells as large as10 cm×10 cm were prepared and characterized following the new co-firing approach. Detailed microstructural, leak-rate testing (gastightness of the sintered electrolyte film) and electrochemical characterizations were carried out. [Copyright &y& Elsevier]

The continuing development of new materials suitable for solid oxide fuel cells operating at about 650–800 °C is of great interest in recent days. The present investigation deals with the development of a perovskite composition–LaNi0.6Fe0.4O3 (LNF)–prepared following two combustion synthesis routes: citrate-gel (LNC) and urea (LNU). The powders were sintered over a wide temperature range (900–1400 °C) and sintering behavior for LNC and LNU was compared. The thermal expansion coefficient (TEC), electrical and microstructural characteristics of LNF was thoroughly investigated. Electrical conductivities were found to be one and a half times higher than that of most commonly used cathode material, La(Sr)MnO3. Moreover, the TEC value of LNF was found to be ≈11.4×10-6 K-1 at 800 °C. The study opens up a possibility of using LNF as a promising cell component for SOFC. [Copyright &y& Elsevier]

The biocompatibility of nickel–titanium alloys was investigated by single-culture experiments on functionally graded samples with a stepwise change in composition from pure nickel to pure titanium, including an Ni–Ti shape memory alloy for a 50:50 mixture. This approach permitted a considerable decrease of experimental resources by simultaneously studying a full variation of composition. The results indicate a good biocompatibility for a nickel content up to about 50%. The cells used in the biocompatibility studies comprised osteoblast-like osteosarcoma cells (SAOS-2, MG-63), primary human osteoblasts (HOB), and murine fibroblasts (3T3). [Copyright &y& Elsevier]