1,720,985 research outputs found
SIMS study of transition metal transport in single crystalline yttria stabilised zirconia
Full text linkThe diffusion of Co, Fe and Ni in single crystalline yttria stabilized zirconia (YSZ) containing 9.5 mol% Y2O3 was studied in the temperature range between 1373 and 1673 K using secondary ion mass spectroscopy. Two different types of diffusion sources were used: thin oxide layers made by spin coating with a thickness of about 150 nm containing all three transition metals (Fe, Co and Ni) on YSZ single crystals and YSZ single crystals implanted with Ni (3 × 1016 ions cm-2, 100 keV) at a mean depth of 45 nm. The determined diffusivities varied in the order D(Fe) < D(Co) < D(Ni). Activation energies for the diffusion of the elements were determined to.be 2.7 ± 0.4 eV, 3.9 ± 0.3 eV and 3.8 ± 0.3 eV for Fe, Co and Ni (3.6 ± 0.5 eV for implanted Ni), respectively. For the latter ion, the value of the activation energy was practically independent of the type of Ni source. The values for all elements were lower by 1-2 eV than for the host cation (Y and Zr) diffusion.Fil: Argirusis, Christos. Technische Universität Clausthal; AlemaniaFil: Taylor, Marcela Andrea. Technische Universität Clausthal; Alemania. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Física La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Física La Plata; ArgentinaFil: Kilo, Martin. Technische Universität Clausthal; AlemaniaFil: Borchardt, Günter. Technische Universität Clausthal; AlemaniaFil: Jomard, François. Centre National de la Recherche Scientifique; FranciaFil: Lesage, Bernard. Université Paris Sud; FranciaFil: Kaïtasov, Odile. Université Paris Sud; Franci
Nitrogen diffusion in nitrogen-doped yttria stabilised zirconia
Full text linkNitrogen self-diffusion was measured in single crystalline nitrogen-doped yttria-stabilised zirconia (YZrON) containing 10 mol% yttrium oxide. Samples containing two different nitrogen contents (5 and 6 mol% N on the anion sublattice) were investigated as a function of temperature (650-1000 K) using implanted N as a stable tracer. For a given temperature, the nitrogen diffusivity was nearly independent of the nitrogen content in the nitrogen-doped yttria-stabilised zirconia, which can be only partially understood using defect chemistry. The activation enthalpy of nitrogen diffusion was between 2 and 2.5 eV with a preexponential factor of the order of 100 cm2 s-1, which corresponds to a migration entropy of 5 kB. The surface exchange reaction between nitrogen and the oxonitride surface was investigated at 1073 K using 200 mbar gaseous 15N2 and was found to be slow but considerable. Decreasing the oxygen content in the gas phase can enhance the nitrogen incorporation into the oxonitrides.Fil: Kilo, Martin. Technische Universität Clausthal; AlemaniaFil: Taylor, Marcela Andrea. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Física La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Física La Plata; Argentina. Technische Universität Clausthal; AlemaniaFil: Argirusis, Christos. Technische Universität Clausthal; AlemaniaFil: Borchardt, Günter. Technische Universität Clausthal; AlemaniaFil: Lerch, Martin. Technishe Universitat Berlin; AlemaniaFil: Kaïtasov, Odile. Universite Paris-sud Xi; FranciaFil: Lesage, Bernard. Centre de Sciences Nucléaires Et de Sciences de la Matière; Franci
Lanthanide transport in stabilized zirconias: Interrelation between ionic radius and diffusion coefficient
Full text linkThe diffusion of all stable lanthanides in calcia stabilized zirconia (CSZ) and in yttria stabilized zirconia (YSZ) was measured. Lanthanide migration enthalpies were calculated using the Mott-littleton approach. The results suggest that the bulk diffusion coefficient depends on the ionic radius of the lanthanide tracer. It was also found that the experimental activation enthalpies are about 6eV for CSZ and between 4 and 5 eV for YSZ and almost constant for all lanthanides.Fil: Kilo, Martin. Technische Universität Clausthal; AlemaniaFil: Taylor, Marcela Andrea. Technische Universität Clausthal; Alemania. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Física La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Física La Plata; ArgentinaFil: Argirusis, Christos. Technische Universität Clausthal; AlemaniaFil: Borchardt, Günter. Technische Universität Clausthal; AlemaniaFil: Weber, Sylvain. École Nationale Supérieure Des Mines de Nancy; FranciaFil: Scherrer, Hubert. École Nationale Supérieure Des Mines de Nancy; FranciaFil: Jackson, Robert A.. Keele University; Reino Unid
Defects and phase transitions in yttria- and scandia-doped zirconia
Full text linkInternal friction (IF) experiments were performed on the systems ZrO 2 (8-12 mol%)-Y2O3, and ZrO2 (9-12 mol%)-Sc2O3. The following features were found: (i) an IF peak around 500 K in both systems which is assigned to the hopping of trapped oxygen vacancies (ΔH=1.2-1.3 eV); (ii) in polycrystalline materials a high temperature damping background, which is related to cation diffusion; (iii) an order/ disorder phase transition at 1450 K in ZrO2-12 mol%Y 2O3; and (iv) in ZrO2-Sc2O 3 a ferroelastic ↔ ferroelectric phase transition at 750 K from the rhombohedral to the cubic phase. Cation diffusion experiments in ZrO 2-Sc2O3 revealed an activation enthalpy for Zr diffusion of 5.3 eV indicating that short- and long-range cation transport is governed by one type of cation diffusion process. © 2004 Elsevier B.V. All rights reserved.Fil: Weller, Manfred. Max-Planck-Institut für Metallforschung; AlemaniaFil: Khelfaoui, Fadila. Max-Planck-Institut für Metallforschung; AlemaniaFil: Kilo, Martin. Institut für Metallurgie; AlemaniaFil: Taylor, Marcela Andrea. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Institut für Metallurgie; AlemaniaFil: Argirusis, Christos. Institut für Metallurgie; AlemaniaFil: Borchardt, Guenter. Institut für Metallurgie; Alemani
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Untersuchungen zur gemeinsamen Hydrierung einer hydrothermal vorbehandelten Braunkohle mit mineralölstämmigen Anmischölen
No full textVariations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
ELECTROPHORETIC DEPOSITION AS A METHOD FOR THE PREPARATION OF CERAMIC FUEL CELLS
Full text linkSolid Oxide Fuel Cells (SOFC) have attracted great attention due to highly efficient electric power generation, system modularity, multi fuel capability and possibility of direct hydrocarbon conversion. Traditional YSZ electrolytes need high operating temperatures at 800-1000°C. Therefore fabrication, long term stability and material costs of these conventional SOFC systems are rather high. Lowering the working temperature is required to make this promising technology commercially viable. YSZ is the standard material to be used as electrolyte in high temperature oxide fuel cells. We developed a simple method for the electrophoretic deposition of electrodes on dense electrolyte substrates. To allow significant temperature reduction new electrolyte materials with higher oxygen ion conductivity below 800°C compared to YSZ are needed. Apatite type lanthanum silicates (ATLS) are a new class of electrolytes which provides good oxygen permeability even at lower temperatures. These new electrolytes necessitate the development of suitable electrode materials. The ATLS electrolyte needs to be dense and gastight allowing only the transport of O2- ions through the electrolyte, whereas the electrodes need to be porous in order to allow gas exchange while maintaining good adhesion to the electrolyte. Another fuel cell class which allows the reduction of the service temperature is based on the use of proton conducting ceramics and we preset the preparation of such fuel cells as well. Electrophoretic deposition of ceramic films has become an attractive alternative for the fabrication of SOFCs, due to the need to control the layer thickness by the order of microns. In this study, we present the preparation of different ceramic fuel cells by electrophoretic deposition
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