1,721,277 research outputs found
Development of electrode materials based on manganese oxides for anodic oxidation of organic pollutants
No full textThe electrodes made of manganese oxides represent an interesting family of materials, which are
today primarily used as cathodes in alkaline batteries and lithium-ion batteries. A so far less studied application is their use as anodes in the electrochemical treatment of compounds toxic and/or refractory to biodegradation. In this research, we present the results related to the electrocatalytic capacity of electrodes formed from films of manganese oxides deposited by chemical or electrochemical way, in the degradation of solutions containing the azo-methyl-orange dye. The electrodes were characterized by morphological analysis and, in order to evaluate the efficiency of electrochemical treatment for decolorization and subsequent mineralization, electrolyses under galvanostatic conditions were conducted in a reactor without separation.
The results obtained show that the electrodes of manganese exhibit similar behavior to the diamond, with the production of hydroxyl radical from the discharge of the water but, unlike these, they have a low production capacity of active chlorine. This characteristic makes them particularly attractive for use in processes where there is an interest in keeping low the production of chloro-compounds. The main limitation found in this initial research was that of a poor adhesion to the substrate and then of an insufficient mechanical stability and durability. We evaluated the influence on the durability and the ability of degradation of various parameters such as: co-presence of other metals, and the thickness of the oxide layer.
The interesting electrocatalytic ability of the manganese oxides combined with the low production of oxy-clorurate species and at low cost, do encourage further research with the aim of improving the stability and durability of these materials by using more efficient preparation techniques
Glyme electrolytes for the new generation of energy storage devices
No full textThe increasing demand of portable energy in terms of cycle life for electronic devices such as smartphones, tablets and computer or the high stability required for medical application and the high energy density for smart energy grids and electrified transport require a breakthrough in performance lower cost, safety and environmental compatibility. indeed, the conventional energy storage devices are characterized by limited specific capacity and energy density due to the intrinsically properties of the cathodic active materials i.e. LiCoO2 with specific capacity if 150 mAhg-1 and a theoretical energy density of 550 WhKg-1. therefore, the deep investigation and optimization of new classes of electrodes proposed in this work of thesis, may shed light on the possible candidates for a new generation of energy storage devices characterized by high energy density and environmental compatibility. Furthermore, one of the main topic of this work is the study of new classes of electrolytes characterized by low flammability and high ion mobility properties in order to ensure high performances and safety leve
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
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
Influence of surface roughening of Titanium substrate in the electrochemical activity of Manganese oxide thin film electrode in anodic oxidation of dye-containing solutions
No full textPrevious work has verified the possibility to obtain mechanically, chemically and electrically stable electrodes based on manganese oxide (MnOx) thin films for anodic oxidation of solutions containing the RV5 azodye. To improve the morphological and electrochemical properties of these materials, in this study, a surface modification of the titanium support has been presented. Chemically modified surfaces were obtained by etching titanium substrates in hydrocloridric acid at high temperature. Untreated and modified electrodes were coated sequentially with a RuOx film, as interlayer and a MnOx film obtained by adopting three different techniques including anodic electrodeposition, cathodic electrodeposition and thermal decomposition. Surface morphology, topography and composition of all the electrodes were investigated by profilometric and TOF-SIMS analysis. Anodes electrochemical activities were first determined by cyclic voltammetry, and then in the treatment of solutions containing the azo dye Reactive Violet 5 (RV5), as model pollutant, in undivided cell under galvanostatic conditions. The results show that the surface microstructure modifies substantially the electrochemical response of selected electrodes
Reactivity of electrogenerated N-heterocyclic carbene in room-temperature ionic liquids. Cyclization to 2-azetidinone ring via C3-C4 bond formation
No full textThe intrinsic chemistry of imidazolium-
based room-temperature ionic liquids, related to the
acidity of the C-2 imidazolium cation, can be modi-
fied via cathodic cleavage of the C-2/hydrogen bond.
N-Heterocyclic carbenes, electrogenerated by elec-
trolysis of imidazolium-based room-temperature
ionic liquids, are stable bases that are strong enough
to deprotonate bromoamides 1a–k yielding the azeti- din-2-one ring via C-3/C
4 bond formation. The
electrosynthesis of b-lactams 2a–k has been achieved
under mild conditions, elevated yields and avoiding
the use of toxic, volatile, molecular solvents
Electrogenerated cyanomethyl anion in organic synthesis: formation of four and five- membered heterocycles
No full text- …
