1,720,973 research outputs found
LSCF and Fe2O3/LSCF powders: interaction with methanol
No full textThis work focalizes on a nanosized La0.6Sr0.4Co0.8Fe0.2O3−δ (LSCF) perovskite and Fe2O3/LSCF nanocomposites. The nanosized LSCF perovskite
is obtained by Pechini method and treated at 1173 K; nanocomposite Fe2O3/LSCF powder samples (Fe2O3/LSCF = 1:9 and 1:1 wt.) are
obtained by wet impregnation.
The reactivity of the obtained samples with respect to pure methanol and to a 1M aqueous solution of methanol, is investigated by means of
IR Spectroscopy and Quadrupole Mass Spectrometry (QMS). In presence of pure methanol the main reaction is methanol decomposition with
the formation of CO and H2. The activity with respect to this reaction starts to be observed at 573K both for the LSCF perovskite and for the
Fe2O3/LSCF nanocomposites and shows an irregular trend as a function of temperature. Steam-reforming reaction is evident at T≥623K when a
1M solution of methanol is used. The reactivity with respect to methanol and to the 1M solution of methanol was also investigated as a function
of time: only at 673K the methanol decomposition starts immediately; the waiting time changes as a function of temperature, sample composition
and reactive mixture. The steam reforming reaction, in contrast, begins immediately
La0.8Sr0.2Ga0.8Fe0.2O3-δ-based SOFCs electrode: effect of the synthetic procedures on properties and reactivity
No full textA Sr and Fe doped lanthanum perovskite is prepared by Pechini procedure and characterized by means of different techniques. The reactivity in alcohol oxidation is also considered for applications in the anode compartment of IT-SOFCs
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
LaSrCoFeO and powders: Synthesis and Characterization
No full textThis work focuses on a La0.6Sr0.4Co0.8Fe0.2O3-ä (LaSrCoFeO) perovskite and Fe2O3/LaSrCoFeO
nanocomposite powders; the samples are characterized by means of X-ray photoelectron spectroscopy
(XPS), X-ray diffraction (XRD), extended X-ray absorption fine structure (EXAFS), diffuse reflectance
infrared Fourier transform (DRIFT) spectroscopy, scanning electronmicroscopy (SEM), and thermal
analysis (TA) and inductively coupled plasma-atomic emission spectroscopy (ICP-AES). The nanosized
LaSrCoFeO perovskite is obtained by Pechini method and is treated at increasing temperature. The
LaSrCoFeO perovskite phase forms at T g 1173 K; at this temperature, traces of La2O3, Co3O4, and
La(2-x)SrxCoO4 are also present. Strontium is surface segregated as SrCO3 and SrO. Nanocomposite Fe2O3/
LaSrCoFeO powder samples (Fe2O3/LaSrCoFeO ) 1:9 and 1:1 wt) are obtained by wet impregnation.
The iron oxide deposition damages the perovskite structure because of the diffusion of iron inside the
perovskite; this is particularly evident from SEM images
La0.6Sr0.4Co1-yFeyO3-d perovskites: influence of the Co/Fe atomic ratio on properties and catalytic activity towards alcohol steam-reforming
No full textLa0.6Sr0.4Co1-yFeyO3-delta (y = 0.2, 0.5, 0.8) perovskite-type oxide powders were prepared by the citrate gel method with the. aim of investigating the influence of cobalt/iron atomic ratio on the chemical and structural properties as well as on the catalytic activity. The samples were characterized by means of X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), thermal analysis, Kr physisorption surface area, scanning electron microscopy (SEM), and temperature programmed reduction (TPR). XRD outcomes reveal the formation of perovskite phase after calcination at 873 K. Depending on the Co/Fe atomic ratio, the perovskite exhibits two different structure: rhombohedral for y = 0.5. However, other phases are also observed. The crystallite size increases with the calcination temperature, while decreases with the iron content. The specific surface area of the La0.6Sr0.4Co1-yFeyO3-delta perovskites (calcined at 1073 K) is low, but increases with the iron amount: it varies between 4.1 and 6.6 in 2 g(-1) moving from y = 0.2 to y = 0.8. XPS results reveal the presence of traces of Co(II) in the sample with lower cobalt amount. The scanning electron micrographs reveal nanoscaled near spherical particles which are clustered together, forming a highly porous microstructure. However, the samples with higher iron content show a more compact morphology due to the enhanced agglomeration. The perovskite phase is rather stable even after aggressive treatment as high temperature reduction. The influence of cobalt/iron atomic ratio on the catalytic activity toward alcohol steam reforming was investigated. All the samples present good alcohol dehydrogenation activity, as resulting from the methanol steam reforming experiments. In the steam reforming of ethanol, the La0.6Sr0.4Co1-yFeyO3-delta presents the better performance (especially after reduction at 873 K) with the complete conversion of ethanol into syngas above 850 K and the almost complete suppression of the ethylene formation at lower temperature. The differences of the activity toward ethanol steam reforming are attributable to a different stabilization of Co(0) nanoparticles produced during the reduction at 873 K
A bis(thiosemicarbazone) bifunctional chelating agent for nitrido-technetium-99m and copper-64 based radiopharmaceuticals
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
Bioactivity property of TiO2 MOCVD coatings on Ti substrates with different pristine morphology
No full textTitanium and its alloys have been widely used for dental implants due to their excellent combination of strength-to-weight ratio, excellent corrosion resistance and biocompatibility [1]. A surface feature of Ti is the capability to spontaneously form a thin (4-6 nm) stable amorphous TiO2 film. Despite the excellent biocompatibility of the native oxide film, this oxide is known to seldom bond chemically to bone tissue [2 and ref. therein]. Various techniques have been developed in order to grow up TiO2 layers with improved characteristics with respect to the native layer: deposited rutile and anatase layers compared to native TiO2 show enhanced bone-like precipitation at the surface in simulated body fluids. MOCVD technique has been applied to the growth of TiO2 coatings, which successfully underwent several biological tests [2 and ref. therein]. However, the influence of the TiO2 MOCVD coating on the bioactivity of Ti substrate with peculiar pristine morphology has been weakly explored. In this regard, besides to the chemical surface composition, the roughness and the topography of the Ti surface are significant parameters that affect the rate and quality of osseointegration. In this work, three types of Ti substrates (machined, sandblasted, and sandblasted/acid etched) with different morphology were coated with 200 nm titanium oxide films by using MOCVD, operating at 350°C and 100 Pa. The influence of the pristine substrate morphology on TiO2 crystalline structure, morphology, surface wettability and bioactivity is here presented. It is shown that the specific morphology of the substrate influences both the crystalline phase of the TiO2 and the crystallite size. SEM analysis shows an optimal conformal coverage of the coating for all substrates, with specific grain size as a function of the substrate morphology. Even the wettability depends on the Ti substrate features, demonstrating a superhydrophilic behaviour for the sandblasted/acid etched samples after MOCVD deposition. Finally, bioactivity experiments were carried out in order to evaluate the influence of substrate morphology on the bioactivity of the TiO2/Ti samples in simulated body fluid (SBF)
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