1,720,969 research outputs found
Mechanical properties and microstructural stability of CuTa/Cu composite coatings
No full textIn this study, the structure and mechanical properties of as-deposited and 823.15 K annealed CuTa coatings were studied with the purpose to evaluate the microstructural and mechanical thermal stability as a function of the Ta content. CuTa coatings with a Ta content from 0 to 100% were prepared by magnetron co-sputtering. Their structure and mechanical properties were characterized by grazing angle X-ray diffraction (XRD), scanning and transmission electron microscopy (TEM), and nanoindentation. The XRD results show that a Ta-rich CuTa glass metal is formed in the coatings with 15–67 at.% Ta along with nanocrystalline Cu and such microstructure was retained after vacuum annealing at 823.15 K. TEM analyses of selected samples showed the formation of crystalline Cu islands in an amorphous CuTa matrix in both as-deposited and annealed coatings. The coatings presented a 3D distribution of Cu nanocrystals within an amorphous CuTa matrix which might reduce the brittleness of the glassy CuTa matrix. A significant increase in hardness values from 0.9 GPa for pure Cu to 11.9 GPa for the sample with 98 at.% Ta is observed. It has been shown that the composite coatings preserved the microstructure and were mechanically stable after vacuum annealing.</p
Spray deposited β-Bi2O3 nanostructured films with visible photocatalytic activity for solar water treatment
No full textEfficient α/β-Bi2O3 composite for the sequential photodegradation of two-dyes mixture
No full textA mixture of α/β-Bi2O3 and α-Bi2O3 powders were obtained by a simple solid state reaction-annealing route at 550 °C. The structure, optical properties and surface area of the commercial α and β-Bi2O3 and the synthesized α-phase and α/β-composite were well characterized by X-ray diffraction, diffuse reflectance spectra and N2 physisorption. The annealed sample at 550 °C showed 20% of β-phase, forming a heterojunction of α/β-Bi2O3 whereas annealing at elevated temperature (650 °C) lead to the α-phase. Optical properties showed that the presence of the β-phase is mainly responsible for narrowing the energy band gap. The photocatalytic activity of the commercial α and β-Bi2O3 and the synthesized α-phase and α/β-composite were investigated in degradation of single dyes, Indigo Carmine (IC) and Rhodamine-B (RhB) under both UV and visible light-induced photocatalysis. For the best photocatalyst, the photodegradation in a two-dye mixture solution was systematically studied considering the type of dye, the adsorption capacity of the samples and the behavior of dye photodegradation. The photocatalytic performance of α/β-Bi2O3 was comparatively much higher than the commercial α and β-Bi2O3, indicating that better performance of efficient charge separation and transfer across α/β-Bi2O3 composite was obtained. Possible mechanism of the single dye and two-dye mixture degradation was given by using α/β-Bi2O3 composite
Tribological response of δ-Bi2O3 coatings deposited by RF-magnetron sputtering
No full textPeer reviewe
Effect of the addition of Si into V<sub>2</sub>O<sub>5</sub> coatings: Structure and tribo-mechanical properties
No full textVanadium oxide (V2O5) is one of the lubricious oxides with the potential to be used as a solid lubricant at elevated temperatures. However, the material itself is not hard wear-resistant, so most of the research has focused on adding V into hard nitride coatings that could lead to the formation of a self-lubricating V2O5 layer when heated. The other possible solution, which has been less studied, is to look for mechanisms to enhance the hardness of the oxide coating. In this research, we investigate the effect of the addition of Si into the V2O5 coatings, aiming to find conditions that lead to enhance hardness and/or reduced wear while keeping the high temperature lubricity of the V2O5 structure. For this, Si modified V2O5 coatings were deposited using a dual magnetron sputtering system. The results showed that small additions of Si (<2.0 at%) improved the hardness of the V2O5 coatings up to 5 times while keeping the same temperature dependence of the coefficient of friction than V2O5. Dry sliding experiments using the pin-on-disc configuration against silicon nitride balls were performed at 25, 300 and 600 °C. Wear factors in the 10−7 mm3/Nm range were obtained, indicating a good wear resistance. Further addition of Si into the V2O5 structure led to a loss of the crystalline ordering and a significant reduction in the hardness.</p
Hydrazine modified g-C3N4 with enhanced photocatalytic activity for degradation of indigo carmine
No full textPolymeric graphitic carbon nitride (g-C3N4) was obtained from urea and modified by heat polymerization at 550 °C in the presence of hydrazine as a modifier agent. The influence of in-situ generated NH3 by hydrazine decomposition at different contents (0.5, 1, 1.5, and 2 mL) on the physicochemical properties and surface properties (water contact angle and point of zero charge) of the g-C3N4 were investigated. The modified g-C3N4 were analyzed by X-ray diffraction, scanning electron microscopy, diffuse reflectance spectroscopy, X-ray photoelectron spectroscopy, photoluminescence, Fourier Transform Infrared, water contact angle, surface area, and the point of zero charge. The in-situ generated NH3 induced an evolution from nano-flakes to lamellar plate morphology depending on stacked interplanar. The influence of surface properties on the photocatalytic response of the unmodified and modified g-C3N4 was tested in the photodegradation of indigo carmine dye at pH = 3.5 and 6.5 solutions under blue LEDs light. The photostability of the samples was tested after 4 cycles of reaction. The properties (surface area (SA); water contact angle (WCA), and optical gap) influence the photocatalytic response, which was summarized in a single parameter defined as SA/(WCA*gap). The maximum value of this product match with results obtained for the most active photocatalyst (U-Hz1).Fil: Valencia, Karen. Universidad Nacional Autónoma de México; MéxicoFil: Hernández Gordillo, Agileo. Universidad Nacional Autónoma de México; MéxicoFil: Mendez Galvan, Melissa. Universidad Nacional Autónoma de México; México. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Biodiversidad y Biología Experimental y Aplicada. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Biodiversidad y Biología Experimental y Aplicada; ArgentinaFil: Morett, Diego. Universidad Nacional Autónoma de México; MéxicoFil: Rodil, Sandra E.. Universidad Nacional Autónoma de México; Méxic
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
Variations 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
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