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Abstract: A simple sol–gel based electrospinning method has been applied for the synthesis of vanadium oxide/polyvinyl acetate (V2O5/PVAC) fibers for gas sensing applications. The pure phase V2O5 has been subsequently obtained by removing the polymer phase via annealing of the composite fibers in air. The as-spun V2O5/PVAC composite fibers and related products of annealing have been widely studied to characterize their morphological and microstructural properties by TG-DSC, XRD, DRIFT and SEM investigations. The application of the produced V2O5 fibers as high performance ammonia resistive sensors has been demonstrated. Reversible electrical changes have been observed by exposing V2O5 fibers deposited on interdigited electrodes to sub-ppm concentrations of ammonia gas. The fabricated V2O5 sensor has shown the highest response to ammonia gas at 200–250°C, with a response and recovery time of about 50 and 350s, respectively. A linear dependence of the response value on the ammonia concentration has been observed in the range of 0.85–8.5ppm, with an estimated lower detection limit of about 100ppb. [Copyright &y& Elsevier]

Abstract: This work describes the low temperature synthesis of novel nanosized Au/La1−x Sr x MnO3 (x ≈0.4) and Au/La0.85Sr0.15CrO3 composites and investigates their potential as anodic catalysts for propane reforming. The pristine La1−x Sr x MnO3 (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 (<5 nm) was deposited on the perovskite powders surface by an ultrasound-driven synthesis. The catalytic behavior of these inorganic composites was investigated for the following propane reforming processes, i.e. steam reforming, partial oxidation and autothermal reforming. Good propane conversions in the partial oxidation conditions were detected for sub-hundred nanometer La1−x Sr x MnO3 perovskite and the role of gold as a promoter for this process was assessed. In particular, nanosized gold on La1−x Sr x MnO3 resulted in an increase of the perovskite stability under all catalysis conditions. The influence of water steam in the feeding gas stream was also tested. The low influence of gold presence in catalytic tests of Au/La0.85Sr0.15CrO3 suggested poor gold catalytic activity in the tested conditions but a presumable role of gold on the stabilization of the Mn mixed oxidation state in the case of the manganites. [Copyright &y& Elsevier]

Abstract: TiO2 nanometric powders were prepared via a sol–gel procedure and calcined at various temperatures to obtain different surface and bulk properties. The calcined powders were used as fillers in composite Nafion membranes for application in high temperature direct methanol fuel cells (DMFCs). The powder physico-chemical properties were investigated by X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and pH measurements. The observed characteristics were correlated to the DMFC electrochemical behaviour. Analysis of the high temperature conductivity and DMFC performance reveals a significant influence of the surface characteristics of the ceramic oxide, such as oxygen functional groups and surface area, on the membrane electrochemical behaviour. A maximum DMFC power density of 350mWcm-2 was achieved under oxygen feed at 145°C in a pressurized DMFC (2.5bar, anode and cathode) equipped with TiO2 nano-particles based composite membranes. [Copyright &y& Elsevier]