1,720,973 research outputs found
The role of palladium salt precursors in Pd-PdO/CeO2 catalysts prepared by dry milling for methane oxidation
No full textEffect of pulse current on wear behavior of Ni matrix micro-and nano-SiC composite coatings at room and elevated temperature
No full textThis work presents the effect of the pulse-current on the wear behavior of Ni/nSiC and Ni/μSiC electrodeposits.
The deposits microstructure and SiC content were investigated by means of microstructural, crystallographic e chemical analysis. The mechanical properties were evaluated through microhardness measurements. Ball-on-disc tests were performed at both room temperature and 300 °C. Wear rate and mechanisms were determined by morphological and microscopical characterization.
The composite-coatings produced under pulse current present enhanced hardness and wear resistance, at both temperatures, linked to microstructural refinement and SiC content. The main wear mechanism observed was triboxidation, accompanied by abrasive wear mainly on the micro-composite coatings
Influence of nanoscale surface arrangements on the oxygen transfer ability of ceria-zirconia mixed oxide
Get PDFCeria-based materials, and particularly CeO2-ZrO2 (CZ) solid solutions are key ingredient in catalyst formulations for several applications due to the ability of ceria to easily cycling its oxidation state between Ce4+ and Ce3+. Ceria-based catalysts have a great soot oxidation potential and the mechanism deeply relies on the degree of contact between CeO2 and carbon. In this study, carbon soot has been used as solid reductant to better understand the oxygen transfer ability of ceria-zirconia at low temperatures; the effect of different atmosphere and contact conditions has been investigated. The difference in the contact morphology between carbon soot and CZ particles is shown to strongly affect the oxygen transfer ability of ceria; in particular, increasing the carbon-ceria interfacial area, the reactivity of CZ lattice oxygen is significantly improved. In addition, with a higher degree of contact, the soot oxidation is less affected by the presence of NOx. The NO oxidation over CZ in the presence of soot has also been analyzed. The existence of a core/shell structure strongly enhances reactivity of interfacial oxygen species while affecting negatively NO oxidation characteristics. These findings are significant in the understanding of the redox chemistry of substituted ceria and help determining the role of active species in soot oxidation reaction as a function of the degree of contact between ceria and carbon
Key Properties and Parameters of Pd/CeO2 Passive NOx Adsorbers
Get PDFIn this paper, a series of Pd/CeO2 catalysts prepared by different synthesis routes and showing different morphological and textural properties have been investigated for passive NOx adsorption (PNA) applications. The results obtained by NOx adsorption/desorption tests demonstrated that NOx storage capacity and NOx storage efficiency of Pd/CeO2 materials depend strictly on their surface area, whereas the morphology of the support and the Pd deposition method do not seem to play a key role. In contrast, the Pd deposition method does impact the dynamics of NOx desorption by affecting the amount of NOx desorbed at different temperatures. This seems to be connected to Pd-Ce interactions at the nanoscale that favor NOx desorption at higher temperatures suitable for PNA application. These findings are relevant in designing and optimizing the properties of Pd/CeO2 materials for their function as passive NOx adsorbers
Synthesis, microhardness, fracture toughness and microstructural features of chitosan containing alkali activated geopolymers
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High stability and activity of solution combustion synthesized Pd-based catalysts for methane combustion in presence of water
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Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Variations on the Author
Get PDF“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
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