Hydrogen sensors on the basis of SnO2-TiO2 systems

AbstractIn this study we compare sensor responses to H2 in air using two types of sensing materials: SnO2 bulk doped with TiO2 and mechanical mixtures of SnO2 and TiO2. The materials were analyzed in the broad range of working temperatures and H2 concentrations. Thermal stability of SnO2 bulk doped with TiO2 was studied by in-situ XRD at 700°C

Identification of Cinnabar by non-Destructive Techniques on a Human Mandible from Carrer Paris Chalcolithic Hypogeum (Cerdanyola del Vallès, Barcelona, Spain)

The Carrer Paris site is located in Cerdanyola del Vallès (Barcelona, Spain). It is a Chalcolithic hypogeum dated between 3800-4100 BP with more than 60 individuals distributed in four burial levels. We study the remains of Individual 5 from burial level II. It is an adult skeleton, preserved in anatomical position and buried with Campaniform pottery. During the excavation, we identified red pigment on the mandibular symphysis region of the individual 5. In this work we present the preservation state and conservation methodology to restore the individual 5 cranium and mandible. At the same time, we present the results of the pigment composition analyzed by non-destructive methods. These analyses were conducted directly on the pigments and the bone surface with environment electronic microscopy (ESEM-EDS) X-ray micro-diffraction (µ-DRX) before the conservation treatments. The objective of the analysis was to characterize the pigments, the bone and the clays to apply the best methodology to conserve the pieces. The combination of both techniques allows us to analyze the area of interest without removing samples. These analyses were performed directly, without affecting the bone and pigments and assuring the integral preservation of the objects. The results reach us new data on the use of pigment in funerary rituals during the Chalcolithic.L’hypogée du Chalcolithique de la Rue Paris (Cerdanyola del Vallès, Barcelona, Espagne) a été daté entre 3800 et 4100 BP. Les restes anthropologiques fouillés étaient distribués sur quatre niveaux et dépassaient les 60 individus. Ceux étudiés ici proviennent du deuxième niveau d’inhumation et appartiennent à un squelette adulte (individu 5), préservé en connexion anatomique et inhumé avec de la céramique campaniforme. Au cours de la fouille, des restes de matière colorante rouge ont été identifiés sur la région de la symphyse mentonnière. Dans ce travail sont présentés l’état de conservation et la méthodologie de restauration du crâne et de la mandibule de l’individu 5. De même, sont présentés les résultats des analyses non destructices faites directement sur les matières colorantes et l’os. Les analyses ont été réalisées avant la restauration du crâne et de la mandibule à l’aide d’un microscope électronique à balayage environnemental (ESEM-EDS) et micro-diffraction de rayons X (µ-DRX). L’objectif des analyses est la caractérisation des pigments, de l’os et du sédiment afin de choisir la meilleure méthodologie à appliquer pour la conservation des pièces. La combinaison de ces techniques favorise l’analyse des zones d’intérêt sans la prise d’échantillons. Ces analyses ont été faites directement sans abîmer l’os ni les pigments et, en conséquence, la préservation intégrale des objets est assurée. Les résultats obtenus apportent une information importante à propos de l’utilisation de quelques matières colorantes dans les rituels funéraires au Chalcolithique

Parametric line profile analysis for in situ XRD of SnO2 materials: Separation of size and strain contributions

10.1016/j.ssi.2013.11.028Parametric line profile analysis has been used to separate size and strain contributions to the peak broadening of in situ X-ray diffractograms recorded during isothermal annealing of nanocrystalline SnO2 materials. Of five kinetic models for isothermal crystallite growth, the simplified generalised parabolic model was found to be the closest to transmission electron microscopy (TEM) crystallite sizes resulting in expected (exponential) relaxation of strain. Crystallite growth and strain evolution of pure and Pd-doped SnO2 has been compared and discussed regarding possible growth mechanisms. It was shown that lattice strain, despite being very low, leads to overestimation of the activation energy for crystallite growth, if not considered in integral breadth analysis

Hydrolysis of dilute acid-pretreated cellulose under mild hydrothermal conditions

10.1016/j.carbpol.2014.04.001The hydrolysis of dilute acid-pretreated cellulose was investigated in a conventional oven and under microwave heating. Two acids - sulfuric and oxalic - were studied. For both hydrothermal conditions (oven and microwave) the resultant total organic carbon (TOC) values obtained by the hydrolysis of the cellulose pretreated with sulfuric acid were higher than those obtained by the hydrolysis of the cellulose pretreated with oxalic acid. However, the dicarboxylic acid exhibited higher hydrolytic efficiency towards glucose. The hydrolysis of cellulose was greatly promoted by microwave heating. The Rietveld method was applied to fit the X-ray patterns of the resultant cellulose after hydrolysis. Oxalic acid preferentially removed the amorphous region of the cellulose and left the crystalline region untouched. On the other hand, sulfuric acid treatment decreased the ordering of the cellulose by partially disrupting its crystalline structure

Actuator response of improved two-way memory TiNi wires evaluated by weight fraction diagrams

10.1007/s11665-014-0933-8This paper experimentally studies the improvement in the actuator response of TiNi shape memory wires brought about by thermal treatments. Heat-treated TiNi wires were thermally cycled at zero stress before being trained by constant stress to develop the two-way shape memory effect. Subsequently, the work output of these two-way memory TiNi shape memory alloys are measured during repeated thermomechanical cycling under various levels of constant stress. Changes in the phase transformation behavior in two-way memory and thermomechanically cycled TiNi shape memory alloy wires are quantified by x-ray diffraction as a function of temperature. The weight fraction diagrams of TiNi wires thermally cycled at zero stress before they were trained suggests that during constant stress training they develop a lower quantity of R-phase than samples that have not been thermally cycled at zero stress before being trained. This gives thermally cycled TiNi samples higher levels of transformation strain and work output during thermomechanical cycling than samples that have not been thermally cycled before training. These results suggest that for the best material performance¿that is, significant transformation strain and, consequently, substantial work output¿the TiNi wire should be thermally cycled at zero stress before training

Cod and Charpy V test data correlation Ferritic steel weld metals

SIGLELD:f82/1959. / BLDSC - British Library Document Supply CentreGBUnited Kingdo

Gas sensing properties of the nanostructured anodic Zr-W oxide film

10.1016/j.snb.2014.08.014The sensing properties of nanostructured Zr-W mixed oxide film have been investigated. The film was prepared via anodizing a sputter-deposited Zr-W alloy layer through nanopores in an anodic alumina layer superimposed on the alloy. The morphology, structure and chemical composition of the film were examined by SEM and XRD. The film consists of an array of self-ordered nanocolumns protruding from a continuous thin oxide layer. The initially amorphous film material crystallizes to monoclinic WO3 and orthorhombic ZrO 2 due to a high temperature annealing in air. A sensor employing the ZrO2-WO3 oxide film as active layer was fabricated and used for detecting various concentrations (1-1000 ppm) of H2, CO, C2H5OH and NO2 at temperatures up to 300 °C. In hydrogen detection experiments, the sensor was very fast, with a response time of 19 s, and highly sensitive to hydrogen, with a response value of up to 50, while showing incomparably weaker and slower responses to carbon monoxide, ethanol and nitrogen dioxide. The features of the films revealed to date are of importance for improving the chemical, structural and exploitation stability of nanostructured tungsten-oxide-based films and their selectivity in hydrogen gas detection

Structure evolution of layered double hydroxides activated by ultrasound induced reconstruction

10.1016/j.clay.2013.08.00

Conversion of glycerol over 10%Ni/y-Al2O3 catalyst

10.1016/j.apcatb.2013.09.02

MEMS-microhotplate-based hydrogen gas sensor utilizing the nanostructured porous-anodic-alumina-supported WO3 active layer

10.1016/j.ijhydene.2013.04.06