1,720,979 research outputs found
Oxidation of organic pollutants on BDD anodes using modulated current electrolysis
No full textIn this paper, a theoretical model is presented for organic pollutants mineralization at high current efficiency (close to 100%) and low energy consumption on boron-doped diamond electrodes. The model is formulated for a perfect mixed electrochemical reactor operated as a batch recirculation system under multiple current steps, in which the applied current is adjusted during the electrolysis to be close to the limiting value. An experimental validation with the anodic oxidation of 3,4,5-trihydroxybenzoic acid is also provided. The results have shown that multiple current steps electrolysis and continuous current control allowed obtaining high oxidation rate and current efficiency
Electrochemical polishing of boron-doped diamond in organic media
No full textThe electropolishing of a boron-doped diamond ~BDD! film deposited by chemical vapor deposition has been studied in acetic acid-H2SO4 media. The electropolished surface has been characterized by scanning electron microscopy ~SEM!, X-ray photoelectron spectroscopy ~XPS!, and electrochemical measurements. The results have shown that in 1 M H2SO4 no polishing of the surface occurred even after prolonged time; on the contrary, in electrolyte containing 3 M acetic acid in 1 M H2SO4 the morphology changed rapidly. The surface became smoother and the roughness decreased as the typical results of a polishing process. All the non-diamond impurities were also removed by the electropolishing treatment in acetic acid media
DSA-type anode based on conductive porous p-silicon substrate
No full textPorous silicon (PS) thin films have been prepared by electrochemical anodization of p-Si in HF–H2O–EtOH solution and they have been used as substrate material for the preparation of iridium oxide based electrodes (PS/IrO2) using the thermal decomposition technique. The morphology and the electrochemical behaviour of the PS/IrO2 have been studied and the results have been compared with IrO2 electrodes deposited on a sandblasted p-silicon (p-Si/IrO2). SEM analyses have revealed that the PS/IrO2 electrodes are porous, rough and IrO2 appears to be deposited within some silicon pores, while the p-Si/IrO2 present a _mud-cracked_ surface. Cyclic voltammetries in 1 M HClO4 have shown that the PS/IrO2 presents higher surface area than p-Si/IrO2
Electrochemical behaviour of fluorinated boron-doped diamond
No full textThe surface properties and the electrochemical behavior of a fluorinated boron-doped diamond ~F-BDD! electrode prepared by plasma treatment in CF4-He mixture has been studied by X-ray photoelectron spectroscopy and cyclic voltammetry in acidic media. The results have shown the presence of carbon-fluorine bonding ~C—CF and C—F! on the surface of F-BDD, which made the surface more hydrophobic. It was also found that hydrogen evolution was shifted to more cathodic potentials for fluorinated diamond, as compared with untreated BDD. Finally, the higher cathodic overpotential for hydrogen evolution permitted nickel deposition and nitrate reduction
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
Electrochemical oxidation of water on synthetic boron-doped diamond thin film anodes
No full textElectrolysis in aqueous 1 M HClO4 and 1 M H2SO4 solutions has been carried out under galvanostatic conditions using boron-doped diamond electrodes (BDD). Analyses of the oxidation products have shown that in 1 M HClO4 the main reaction is oxygen evolution, while in H2SO4 the main reaction is the formation of H2S2O8. In both electrolytes small amounts of O3 and H2O2 are formed. Finally, a simplified mechanism involving hydroxyl radicals formed by water discharge has been proposed for water oxidation on boron-doped diamond anode
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
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
DSA-type anode based on conductive p-Silicon substrate
No full textIn the search for a good dimensionally stable anode-type electrode, p-silicon ~1-3 mV cm! has been chosen as the substrate material due to its high anodic stability and its reasonable cost compared to titanium and tantalum. Several p-Si/IrO2 electrodes have been prepared by thermal decomposition at different temperature. The effect of preparation temperature on the morphological and electrochemical properties has been investigated by scanning electron microscopy analysis, X-ray diffraction, and cyclic voltammetries in 1 M HClO4 showing that p-Si/IrO2 prepared at 450°C presents a high surface area and a low degree of crystallinity, while increasing the calcination temperature resulted in a decrease of true area and an increase in crystallite size. The activity of p-Si/IrO2 electrodes for simple electron transfer reactions and for complex electrode reactions has been also studied by cyclic voltammetry and linear polarization in solutions containing the hydroquinone/benzoquinone redox couple and various organic compounds ~isopropanol, tert-butanol, methanol!. Finally, the anodic stability of a p-Si/IrO2 electrodes prepared at 450°C has been tested by an accelerated service life test. p-Silicon based electrodes were shown to have the highest standardized service life compared with that of titanium- or tantalum-based electrodes
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