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International audience; Droplet volume and temperature affect contact angle significantly. Phase change heat transfer processes of nanofluids – suspensions containing nanometre-sized particles – can only be modelled properly by understanding these effects. The approach proposed here considers the limiting contact angle of a droplet asymptotically approaching zero-volume as a thermophysical property to characterise nanofluids positioned on a certain substrate under a certain atmosphere.Graphene oxide, alumina, and gold nanoparticles are suspended in deionised water. Within the framework of a round robin test carried out by nine independent European institutes the contact angle of these suspensions on a stainless steel solid substrate is measured with high accuracy. No dependence of nanofluids contact angle of sessile droplets on the measurement device is found. However, the measurements reveal clear differences of the contact angle of nanofluids compared to the pure base fluid.Physically founded correlations of the contact angle in dependency of droplet temperature and volume are obtained from the data. Extrapolating these functions to zero droplet volume delivers the searched limiting contact angle depending only on the temperature. It is for the first time, that this specific parameter, is understood as a characteristic material property of nanofluid droplets placed on a certain substrate under a certain atmosphere. Together with the surface tension it provides the foundation of proper modelling phase change heat transfer processes of nanofluids.

Ceria was deposited onto boron doped polycrystalline diamond (BDD) cathodes, through electrochemically induced precipitation from nitrate-based solutions. The deposits were characterized using SEM-EDS, HRTEM, XRD and XPS. The morphology, thickness and composition of ceria films, which besides CeO2 contained Ce(OH)(3) when prepared at very negative potential, were controlled by tuning the deposition parameters. Thin Ce(OH)(3)-free ceria films allowed CO2 electrochemical reduction at overpotentials below 50 mV, yielding formic acid with faradaic yield higher than 40% and stable performance for many hours. Ceria seemed to act as a co-catalyst that activated CO2 for reduction at the H-terminated BDD surface, because comparable results were not obtained with ceria-coated glassy carbon electrodes.

Membranes based on zeolites have been extensively studied and used to purify/separate H2 or CO2 or other gases, depending on their composition. The deposition of zeolite films onto porous, chemically and thermally stable, substrates can increase their stability, but the production process may require lengthy two-step procedures. In this work, a single-step method was developed for the production of homogeneous hydroxy-sodalite (HS) zeolite films, without seeding and by direct deposition during hydrothermal treatment on cheap and porous alumina substrates. Alumina substrates have been developed with fine porosity (> 35% porosity, 500-600 nm of mean pore diameter), with low resistance to gas flow but reduced surface porosity to favour the deposition of dense films. The single-step growth of HS films with a thickness ranging from a few to 28 ?m on alumina was successfully achieved. These membranes have been tested in hydrogen, methane, carbon dioxide and nitrogen, and good results in terms of hydrogen permeance and separation performance were achieved for 10-12-?m-thick HS films on alumina.

The goal of the study was to identify the environmental hotspots of an experimental research work at lab scale consisting in the physical vapor deposition magnetron sputtering of aluminum titanium nitride based thin coatings onto commercial laminated steel. The findings can provide useful insights for supporting the design of future experimental research campaigns, or instrumentation set-ups, with lower environmental impacts. Results highlighted that the main driver of impacts in the analyzed laboratory activities was the electricity used for instruments operations, in particular for the vacuum keeping. Thus, several optimization strategies were evaluated to reduce the overall electricity consumption, and to improve the environmental profile of experimental activities.

Galvanic displacement reactions between sacrificial oxide layers and metal cations, leading to the formation of secondary oxide layers, have been studied with the aim of collecting new experimental evidence on their mechanism. The study has been carried out by combining electrochemical methods, SEM-EDS and XPS depth profiling. Both porous and compact PbO2 layers have been used as sacrificial oxides and reacted, in different experiments, with: (i) a single low-valent cation, (ii) two cations in sequential exchange reactions or (iii) two cations simultaneously. The experimental results converged to show (i) a lack of correlation between the reaction driving force and the secondary oxide growth rate, (ii) the incorporation of cations from solution at the secondary oxide/electrolyte interface, (iii) the transport of Pb species through the growing secondary oxide layer and (iv) a major effect of mass transport on the growth rate.

The electrochemiluminescence (ECL) performances were comparatively investigated at flat and nanoporous gold (NPG) electrodes of different thicknesses (120 and 200 nm) and roughness factors (fr). The phenomena were studied using either tripropylamine (TPrA) or peroxydisulfate (S2O82−) as sacrificial coreactant and Ruthenium (II)-tris(2,2′-bipyridine) as emitting species. The experiments performed using TPrA showed, at first glance, a linear dependence of the ECL emission with respect to the effective surface area of the NPG electrodes. However, ECL signals were not stable in the measuring conditions, presumably due to amine absorption on the metal surface, leading to electrode corrosion and modification of the surface morphology. The experiments made using peroxydisulfate as coreactant provided conversely a stable ECL response, about proportional to the effective electrode surface area, in the considered range of thicknesses.

Pt-based structured catalysts for the low-temperature combustion of methanol have been prepared by electrochemical methods, using Fe-Cr-Al alloy (Fecralloy) foam supports. Among the strategies investi- gated, pulsed electrodeposition of Pt nanoparticles from an H2PtCl6 solution, followed by cathodic elec- trodeposition of CeO2 thin films from a nitrate bath was the most successful. Pt loading and surface area were measured by ICP-MS and cyclic voltammetry, respectively. Although the presence of a CeO2 film decreased the Pt surface area accessible to electrolyte it enhanced the performance of the catalysts towards methanol combustion, without affecting the activation energy of the process, due to the forma- tion of additional active sites along the interface of CeO2-coated Pt nanoparticles

This research aims at studying the stability and thermophysical properties of nanofluids designed as dispersions of sulfonic acid-functionalized graphene nanoplatelets in an (ethylene glycol + water) mixture at (10:90)% mass ratio. Nanofluid preparation conditions were defined through a stability analysis based on zeta potential and dynamic light scattering (DLS) measurements. Thermal conductivity, dynamic viscosity, and density were experimentally measured in the temperature range from 283.15 to 343.15 K and nanoparticle mass concentrations of up to 0.50% by using a transient plate source, a rotational rheometer, and a vibrating-tube technique, respectively. Thermal conductivity enhancements reach up to 5% without a clear effect of temperature while rheological tests evidence a Newtonian behavior of the studied nanofluids. Different equations such as the Nan, Vogel-Fulcher-Tamman (VFT), or Maron-Pierce (MP) models were utilized to describe the temperature or nanoparticle concentration dependences of thermal conductivity and viscosity. Finally, different figures of merit based on the experimental values of thermophysical properties were also used to compare the heat transfer capability and pumping power between nanofluids and base fluid. Ministerio de Economía y Competitividad | Ref. ENE2014-55489-C2-2-R

This paper describes the cathodic electrodeposition of nickel hydroxides from NiCl2 at constant potentials. In a single-compartment electrochemical cell, the procedure yields black films that have the appearance of glassy carbon. XPS analyses reveal that the films consist of a mixture of Ni(OH)2 and NiOOH in a proportion that depends on the deposition potential; furthermore, SIMS analyses indicate that the coatings are richer in NiOOH in the inner regions towards the support. The electrochemical behavior has been compared with data obtained on electrodes based on pure Ni(OH)2 prepared by cathodic electrodeposition from Ni(NO3)2, following literature procedures. This comparison confirms the composite nature of black nickel hydroxide (BN) coatings, adding that Ni(OH)2 and NiOOH are present in nearly equal amounts. The electrocatalytic activity of BN electrodes was tested in the oxidation of methanol in alkaline solutions. Experimental results are consistent with a mechanism previously proposed in literature for the oxidation of organic compounds on nickel electrodes. Comparison with electrodes based on pure Ni(OH)2 shows that, in the low potentials region, the presence of a high amount of NiOOH causes a decrease of activity, while an opposite effect is observed when the potential is increased. The black nickel electrodes show a remarkable stability in repeated cycles of oxidation of methanol and O2 evolution; under similar conditions, conventional Ni(OH)2 films show an appreciable decrease in thickness, as evidenced by the decrease of peak charge in cyclic voltammetry experiments.

Magnesium silicide (Mg2Si)-based alloys are promising candidates for thermoelectric (TE) energy conversion for the middle to high range of temperature. These materials are very attractive for TE research because of the abundance of their constituent elements in the Earth’s crust. Mg2Si could replace lead-based TE materials, due to its low cost, nontoxicity, and low density. In this work, the role of aluminum doping (Mg2Si:Al = 1:x for x = 0.005, 0.01, 0.02, and 0.04 molar ratio) in dense Mg2Si materials was investigated. The synthesis process was performed by planetary milling under inert atmosphere starting from commercial Mg2Si pieces and Al powder. After ball milling, the samples were sintered by means of spark plasma sintering to density >95%. The morphology, composition, and crystal structure of the samples were characterized by field-emission scanning electron microscopy, energy-dispersive spectroscopy, and x-ray diffraction analyses. Moreover, Seebeck coefficient analyses, as well as electrical and thermal conductivity measurements were performed for all samples up to 600°C. The resultant estimated ZT values are comparable to those reported in the literature for these materials. In particular, the maximum ZT achieved was 0.50 for the x = 0.01 Al-doped sample at 600°C.

A high temperature test rig to simultaneously measure electrical conductivity and thermopower is described. The apparatus allows to perform measurements in controlled atmosphere or vacuum to protect oxygen sensitive materials. A spring load mounting placed in a cold zone permits to reduce the thermal contact resistance between the sample and two metallic blocks (the hot side and the heat sink) even at high temperature. The hot side metal block is periodically heated to obtain the thermopower from the slope of the ?V vs ?T line. Conductivity is measured before each thermopower measurement by a linear four-wire method. The automatic data acquisition and analysis is controlled by a LabView-based interface. Two interchangeable setups are possible. The first one uses silver blocks and K-type thermocouples and is suitable for temperatures from 300 to about 1100 K. The second one uses W blocks and S-type thermocouples to allow higher temperatures measurements since all the hot zone parts are made of Al2O3, Pt or W. The device was tested using PdAg alloy and Ni rods and, for the low temperatures range, the NIST Standard Reference Material 3451 (bismuth telluride), strictly confirming the reference data.

International audience; New 3D electrodes are prepared and tested in reductive herbicide dechlorination as the first step of an environmental remediation process. Commercial nickel foams are modified through the spontaneous deposition of silver nanoparticles. Some of the solutions of Ag+ ions employed in the galvanic displacement reactions contain complexing agents, such as thiosulfate or thiocyanate, and a capping agent, polyvinylpyrrolidone (PVP), which influences the morphology and growth kinetics of the silver deposits. Modified foams are used as cathodes for the reductive dechlorination of Alachlor(TM), a common chloroacetanilide herbicide, in a series of tests that confirm the catalytic activity of silver. Electrodes prepared in a thiosulfate solution containing PVP allow extensive reduction of Alachlor(TM) to give deschloroalachlor as the only dechlorinated product.

Magnesium silicide (Mg2Si) is a promising candidate for thermoelectric energy conversion due to its low toxicity, the abundance of its raw constituents and its low density, allowing manufacturing of light, sustainable and relatively cheap devices. Mg2Si needs to be doped in order to increase its efficiency, making this material competitive among materials operating in the intermediate temperature range. In this work, a synthesis procedure based on melting of the raw elements in easily available and cheap Al2O3 crucibles was developed to obtain polycrystalline Sb doped Mg2Si materials in a wide range of compositions. Powders from the crushed lumps were consolidated via spark plasma sintering and then thermally annealed to obtain dense pellets of Sb:Mg2Si with Sb = 0.0, 0.1, 0.3, 0.5, 0.7, 1.0 and 1.5 at%. The effects of Sb doping and of the synthesis and sintering technique on composition, morphology and stability of n-type Mg2Si are discussed. Transport properties (Seebeck coefficient, electrical and thermal conductivity, charge carrier density) were evaluated in order to elucidate the composition–property relationship within this material system and find the optimal doping amount to optimize its thermoelectric properties.

In this work, BaCe0.65Zr0.20Y0.15O3−δ powders with a perovskite-type structure were successfully synthesized by a microwave-assisted sol–gel Pechini method (SGP). By comparison, powders having the same nominal stoichiometry were also prepared without the microwave assistance. For the syntheses, nitrates were used as metal precursors, and ethylenediaminetetraacetic acid and ethylene glycol were used as complexing and polymerizing agents, respectively. An extensive structural and morphological investigation by means of X-ray diffraction (XRD) and scanning electron microscopy (SEM) has been performed. Moreover, in order to check the phase transitions, simultaneous thermogravimetric and differential thermal analyses were (TG-DTA) performed on gels. With respect to the conventional Pechini method, the microwave-assisted process guaranteed a faster, energy-saving procedure for obtaining single-phase nanopowders of high purity. Moreover, a significant increase in pellet densities was achieved owing to a higher grain coalescence.

The La0.75Sr0.25Cr0.5Mn0.5O3-δ (LSCM) catalyst and the novel Ru/La0.75Sr0.25Cr0.5Mn0.5O3-δ composite were investigated as alternative anodes for the direct utilization of propane in anode-supported solid oxide fuel cells. In particular, their synthesis and performance in direct propane reforming were studied. The LSCM powders were prepared by a sol–gel method based on a modified Pechini procedure. Single-phase LSCM perovskite powders were obtained. SEM micrographs of the LSCM powders revealed particles in the 200–300 nm range with a homogeneous grain distribution. The deposition of 5 wt.% metallic ruthenium nanoparticles on the LSCM perovskite powders was carried out by a microwave-assisted procedure. TEM investigations of Ru/LSCM composites showed a homogeneous distribution of metallic ruthenium nanoparticles with a mean grain size of around 2–3 nm. The catalytic activity of these potential anode materials was investigated for the following propane reforming processes: steam reforming (SR), autothermal reforming (ATR) and partial oxidation (POX) at 600, 700 and 800 °C. Very high propane conversion rates were observed under POX and ATR conditions at 700 and 800 °C for both the LSCM and Ru/LSCM compounds (> 92 at 700 °C and > 98% at 800 °C), whereas in the steam reforming environment, a satisfactory conversion was achieved only at 800 °C. The ruthenium presence was found to strongly improve the selectivity for H2 and syngas production for all of the experiments performed, reaching an approximately 90% syngas yield. Finally, good chemical stability after the catalytic tests was demonstrated for the LSCM and Ru/LSCM anode materials.

Single walled carbon nanohorns (SWCNHs) are a black nanoscale spherical aggregate of cylindrical tubes of graphitic carbon which differ from nanotubes in their "horn-like" shape. Their peculiar structure makes them one of the best electronconductors at a nanoscale level. Although not commercially exploited, their rapid environmental diffusion is expected to rise significantly in the next few years. Therefore, we appraised the ecotoxicology of SWCNH powders by taking into account the ecological role of the two species that were deployed in exposure experiments: polychaetes, Hediste diversicolor, and mussels, Mytilus galloprovincialis. Adult mussels and polychaetes were exposed to three SWCNH concentrations: 1, 5, and 10 mg L-1 and acute effects were measured after 24 and 48 h. Sub-lethal effects were estimated at level of physiological functions such as digestion in mussels (i.e. variations in lysosomal parameters and lipofuscin content) and the antioxidant system in both species (i.e. glutathione peroxidase activity and malondialdehyde content). SWCNH suspension in sea water was also characterised, highlighting the formation of aggregates the size of which was related to SWCNH concentrations and their resident time in the medium. The results showed that SWCNH affected the oxidative and lysosomal systems on the hepatopancreas and led to lysosomal alterations on haemocytes in mussels. The biological responses were less clear in polychaetes. This preliminary investigation highlighted the need of focusing future research efforts on possible physiological impairments caused by long-term exposure to SWCNHs in marine species. (C) 2013 Elsevier B.V. All rights reserved.

The influence of different RuO(2) crystallite sizes was investigated by secondary ion mass spectrometry (SIMS) on the oxide deposited on various support materials (Ni, Ti, Al(2)O(3), oxidized Si(100)). In order to examine the effect of an oxidic environment on the film structure, RuO(2) 20%-TiO(2) 80% at. mixed oxide was deposited on Ti. The polycrystalline coatings were prepared by heating the Ru (and Ti)-containing solution dropped on the supports.1 RuO(2) nanocrystalline coatings were grown by chemical vapor deposition (CVD) from Ru(COD)(eta(3)-allyl)(2).2 The identification of mixed oxide clusters showed the higher reactivity of Ni and Al(2)O(3) over the other substrates. Diffusion and migration characteristics were observed to be influenced by the nature of the support. The results are complementary to those of a previous SIMS investigation.3 Copyright 2000 John Wiley & Sons, Ltd.

The IrO(2)/RuO(2)/TiO(2) ternary system is well known for its electrocatalytic activity towards oxygen- and chlorine-evolution reactions. Electrochemical processing induces noticeable chemical and morphological modifications on these electrodes, depending on the noble metal oxide content. In this work, cathodic/anodic polarization and the oxygen-evolution reaction were studied in order to evaluate the electrocatalytic activity at various noble metal oxide percentages. The best performing electrode (30 mol% noble metal oxides) was analyzed before and after electrochemical tests by means of secondary ion mass spectrometry (SIMS) in order to determine the chemical composition modification which occurred on the surface and in deeper regions of the mixed-oxide film.

Oxide incorporation into thermoelectric Mg2Si-based materials was performed starting from commercial Mg2Si and commercial metal oxides by applying ball milling and spark plasma sintering (SPS) processing. The SPS conditions, such as sintering temperature, pressure, and holding time, were optimized with the aim of obtaining both full densification and oxide incorporation. Thermoelectric characterizations, such as Seebeck coefficient and electrical and thermal conductivity, were carried out and related to the pellet compositions. The morphology, composition, and crystallographic structure of the samples were characterized by field-emission scanning electron microscopy, energy-dispersive spectrometry, and x-ray diffraction analyses, respectively.

Multilayered molybdenum silicide-based thin films were deposited via radio frequency magnetron sputtering in order to obtain efficient barrier against oxidation process which affected Mg2Si thermoelectric materials at middle–high temperatures. X ray diffraction, energy dispersive spectroscopy, secondary ion mass spectroscopy, field emission scanning electron microscopy (FE-SEM) and electrical measurements at high temperature were carried out in order to obtain, respectively, the structural, compositional, morphological and electrical characterization of coatings. Furthermore, the mechanical behavior of the thin film/Mg2Si-pellet system was observed in situ as a function of temperature by FE-SEM employing a heating module. Moreover, the barrier properties for oxygen protection after thermal treatment in air at high temperature were qualitatively evaluated.

The Mg2Si-based alloys are promising candidates for thermoelectric energy conversion in the middle-high temperature range in order to replace lead compounds. The main advantages of silicide-based thermoelectrics are the nontoxicity and the abundance of their constituent elements in the earth crust. The drawback of such kind of materials is their oxygen sensitivity at high temperature that entails their use under vacuum or inert atmosphere. In order to limit the corrosion phenomena, nanostructured multilayered molybdenum silicide-based materials were deposited via RF magnetron sputtering onto stainless steel, alumina and silicon (100) to set up the deposition process and then onto Mg2Si pellets. XRD, EDS, FE-SEM and electrical measurements at high temperature were carried out in order to obtain, respectively, the structural, compositional, morphological and electrical characterization of the deposited coatings. At the end, the mechanical behavior of the system thin film/Mg2Si-substrate as a function of temperature and the barrier properties for oxygen protection after thermal treatment in air at high temperature were qualitatively evaluated by FE-SEM.

At present, literature data on viscosity of nanofluids are still scarce and controversial. The possible non-Newtonian behaviour of these fluids is frequently neglected and the problems related to the nanofluids stability and the actual composition are often not considered. In this paper, viscosity data for nanofluids formed by water, as base fluid, and solid nanoparticles of two different materials – single wall carbon nanohorn (SWCNH) or titanium dioxide (TiO2) – are presented. Viscosity was measured by using a rheometer and obtained as a function of the nanoparticles mass fraction and the shear rate, thus allowing evaluation of the possible non-Newtonian behaviour for the nanofluid. Both the studied nanofluids showed a Newtonian behaviour. The viscosity data were correlated by different equations and here an empirical correlation is proposed.

In the recent years, great interest has been devoted to the unique properties of nanofluids. The dispersion process and the nanoparticle suspension stability have been found to be critical points in the development of these new fluids. For this reason, an experimental study on the stability of water-based dispersions containing different nanoparticles, i.e. single wall carbon nanohorns (SWCNHs), titanium dioxide (TiO2) and copper oxide (CuO), has been developed in this study. The aim of this study is to provide stable nanofluids for selecting suitable fluids with enhanced thermal characteristics. Different dispersion techniques were considered in this study, including sonication, ball milling and high-pressure homogenization. Both the dispersion process and the use of some dispersants were investigated as a function of the nanoparticle concentration. The high-pressure homogenization was found to be the best method, and the addition of n-dodecyl sulphate and polyethylene glycol as dispersants, respectively in SWCNHs-water and TiO2-water nanofluids, improved the nanofluid stability.

The Mg2Si-based alloys are promising candidates for thermoelectric energy conversion for the middle high range of temperature. They are very attractive as they could replace lead-based compounds due to their low cost and non toxicity. They could also result in thermoelectric generator weight reduction (a key feature for the automotive application field). The high value of thermal conductivity of the silicide-based materials could be reduced by increasing the phonon scattering in the presence of nanosized crystalline grains without heavily interfering with the electrical conductivity of the thermoelectric material. Nanostructured materials were obtained under inert atmosphere through ball milling, thermal treatment and spark plasma sintering processes. In particular, the role of several bismuth doping amounts in Mg2Si were investigated (Mg2Si:Bi=1:x for x=0.01, 0.02 and 0.04 M ratio). The morphology, the composition and the structure of the samples were characterized by FE-SEM, EDS and XRD analyses after each process step. Moreover, the Seebeck coefficient analyses at high temperature and the electrical and thermal conductivity of the samples are presented in this work. The nanostructuring processes were affect by the MgO amount increase which influenced the thermoelectric properties of the samples mainly by reducing the electrical conductivity. With the aim of further increasing the scattering phenomena by interface or boundary effect, carbon nanostructures named Single Wall Carbon Nanohorns were added to the Mg2Si in order to produce a nanocomposite material. The influence of the nanostructured filler on the thermoelectric material properties is also discussed.

The optical characterization is reported of a new fluid consisting of single-wall carbon nanohorns and ethylene glycol for solar energy applications. Carbon nanohorns play a significant role in enhancing sunlight absorption with respect to the pure base fluid. The obtained results are compared with those obtained for fluids suspending more conventional carbon forms, i.e. carbon-black particles. We found that nanohorn spectral features are far more favorable than those of amorphous carbon for the specific application. This result shows that carbon nanohorn-based nanofluids can be useful for increasing the efficiency and compactness of thermal solar devices, reducing both environmental impact and costs.

Nanotechnologies offer the opportunity to improve the characteristics of the oil and the oil–refrigerant mixture in refrigeration and air conditioning equipments by dispersing nanoparticles in the oil. Here a study of the influence of the dispersion of single wall carbon nanohorns (SWCNH) and titanium dioxide (TiO2) on the tribological properties of a commercial POE oil is presented, together with the effects on the solubility of R134a at different temperatures. The results obtained showed that the tribological behaviour of the base lubricant here considered can be either improved or worsen, depending on the property (anti-wear or extreme-pressure behaviour), by adding small amount of nanoparticles. On the other hand, nanoparticles dispersion in the base oil did not affect significantly the solubility, suggesting the independence of the thermodynamic properties of the oil from the presence of nanoparticles.

Proton conducting electrolyte materials are promising candidates for the development of low temperature solid oxide fuel cells. Among them, various doped barium cerate compounds, such as BaCe1-xYxO3-δ, have been intensively investigated because of their high proton conductivity. As a drawback, cerates are chemically unstable in CO2-containing atmospheres, such as in case of hydrocarbon or syngas fuelled fuel cells. Conversely, doped barium zirconates electrolyte materials exhibit high chemical stability but lower proton conductivity. A goal of this work was to obtain full-density proton conducting materials having both high conductivity and good chemical stability. In particular, the compositions investigated in this work were BaCe1-x-yZrxYyO3-δ (x=0, 0.1, 0.2, 0.3, 0.4; y=0.15, 0.20). The partial substitution of Ce by Zr in doped barium cerate considerably increased their chemical stability in CO2 atmosphere without sensibly affecting the conductivity.

High-temperature proton conductors are promising as electrolytes for intermediate-temperature solidoxide fuel cells. Among them, BaCeO3-based materials have high proton conductivity but rather poor chemical stability. In contrast, barium zirconates are rather stable, but have poorly reproducible densities and conductivities. In this study, the investigation of BaCe1-x-yZrxYyO3-d solid solutions (x = 0, 0.10, 0.20, 0.30, 0.40; y = 0.15, 0.20) was undertaken, with the final aim of finding a composition having both high conductivity and good stability. The influence of the modified sol–gel Pechini synthetic approach on the powder morphology, and of a barium excess on the densification were demonstrated. Single-phase perovskite powders were prepared and high density pellets were obtained at temperatures lower than those commonly employed. Stability tests demonstrated that the Zr introduction into doped barium cerate greatly enhanced the chemical stability, particularly for Zr - 20%. The proton conductivities, measured in a humidified H2/Ar atmosphere by impedance spectroscopy, were only slightly influenced by the Zr amount. Overall, BaCe1-x-yZrxYyO3-d solid solutions having Zr ca. 20-40% and Y ca. 15-20% showed good chemical stability and high conductivity.

This work describes the low temperature synthesis of novel nanosized Au/La1-xSrxMnO3 (x ~ 0.4) and Au/La0.85Sr0.15CrO3 composites and investigates their potential as anodic catalysts for propane reforming. The pristine La1-xSrxMnO3 (x ~ 0.4) and La0.85Sr0.15CrO3 were prepared by a modified nitrate–citrate Pechini method and the process was optimized in order to obtain high surface area perovskite powders. These materials with nanometric or sub-micrometric grain size have been isolated as a single-phase and used for the preparation of the composite. A homogenous distribution of nanosized gold particle (

The passivating effects produced on Ni 49 Ti 51 (at.%) shape memory alloy by electropolishing in methanol–sulphuric acid electrolyte or thermal treatment in air are investigated with ion-beam techniques (secondary ion mass spectrometry (SIMS) and mass resolved ion scattering spectrometry (MARISS)) and electrochemical techniques (polarisation curves, photocurrent spectroscopy and impedance). Electropolishing produces a limited passivation due to formation of a thin layer of amorphous TiO 2 , which causes only a slight hindrance to the oxygen evolution reaction. Thermal treatment in air at 450 °C causes a more substantial passivation due to formation of a thick oxide layer, estimated at about 80 nm for a 16 h treatment on the basis of weight increase, disregarding roughness. Data indicate that the film produced by thermal oxidation has probably a duplex structure, with a porous outer layer with inclusions of Ni species and a compact inner layer, in contact with the substrate, consisting of (essentially) nickel free TiO 2 rutile.

Several antimony- and antimony-platinum-doped tin dioxide electrodes supported on titanium have been characterized by X-ray photoelectron spectroscopy (XPS) for surface analysis and secondary-ion mass spectrometry (SIMS) for in-depth profile analysis. The surface analysis of the freshly prepared electrodes indicates that the Sb/Sn ratio in the electrode surface is similar to the nominal composition in the precursor solution, but the amount of R is higher than this nominal composition. The presence of platinum also produces the segregation of Sb near the electrode surface. The anodic polarization treatment of the electrode produces changes in its chemical state. The growth of a passivating hydroxide in the outer layer is the main cause of the deactivation of Ti/SnO2-Sb electrodes. The introduction of platinum in the layer prevents the hydroxide formation and modifies the deactivation mechanism of the electrode. The growth of an isolating TiO 2 between the support and the active oxide produces the deactivation of Ti/SnO2-Sb-Pt electrodes.

In order to study new and convenient sol–gel syntheses to homogeneous nanocomposites systems based on zinc sulphide clusters embedded in films of silica glass, a thiourea-functionalized silane ((EtO) 3 Si(CH 2 ) 3 NHC( S)NHPh, SilTu) was investigated as starting precursor. Electrospray ionization mass spectrometry (ESI-MS), FT-IR and NMR spectroscopies clearly evidence that SilTu coordinates Zn 2+ ions in solution through the thiourea function. Both zinc acetate (Zn(CH 3 COO) 2 ) and zinc chloride (ZnCl 2 ) were used as zinc source. The SilTu Zn 2+ complex is also stable under sol–gel conditions. Alcoholic solutions of SilTu, zinc acetate and tetraethoxysilane Si(OEt) 4 (TEOS) were used to prepare the thin films by dip-coating. Transparent, homogeneous and crack-free layers were obtained under annealing up to 600 °C. The samples were investigated by X-ray photoelectron spectroscopy (XPS) and secondary ion mass spectrometry (SIMS). Beside ZnS formation, the presence of oxygenated zinc species was observed inside the silica matrix.

DSA metal oxide electrodes such as the RuO(2)/IrO(2)/TiO(2) mixed system are widely studied for their excellent electrocatalytic activity. In order to understand their catalytic properties, the comprehension of the surface chemistry involved during electrochemical treatments is crucial. With this aim, RuO(2)/IrO(2)/TiO(2) mixed-oxide electrodes having various noble metal contents were studied by means of secondary ion mass spectrometry (SIMS). In particular, cathodic and anodic polarization and O(2) evolution reactions were carried out to test the electrode behaviour and SIMS analyses were performed after all these treatments. In this way, surface changes induced by electrochemical treatments and depending on electrode composition were widely investigated by SIMS, revealing, for example, the presence of hydration or preferential dissolution phenomena induced by electrochemical processing.

This paper is concerned with the study of metallorganic chemical vapor deposition (MOCVD) anatase film growth, with the aim of assessing the relationship between the TiO2 surface morphology and the photocatalytic properties of the films, particularly their relation to the decomposition of ethylbenzene at 50 mu g m(-3) in humidified air. We have found an interesting relationship between the structural properties of TiO2 films deposited by MOCVD at 400 degrees C for different deposition times. We observed the maximum efficiency of films in the thickness range of 600-900 nm, while in a higher thickness, this activity relentlessly decreased. From atomic force microscopy analysis, it was ascertained that this reduction was not due to a decrease in the superficial area, which showed a constant roughness of films thicker than 600 nm. From X-ray diffraction analysis, the films always grew in the anatase TiO2 structure, but the thicker the films, the more pronounced the (100) preferred orientation. Thanks also to theoretical considerations, it was concluded that the activity decrease in the 900-1800 nm thickness range was due to the particularly strong increase in the (100) plane-oriented crystallites recorded in the same range, causing a decrease in surface energy and, contemporaneously, a hindering effect on photocatalytic activity.