1,721,100 research outputs found
Express and low-cost microwave synthesis of the ternary Chevrel phase Cu2Mo6S8 for application in rechargeable magnesium batteries
No full textThe ternary Chevrel phase Cu2Mo6S8 was successfully synthetized using a simple and cost-effective solid-state microwave-assisted reaction. While solid-state routes require days of high-temperature treatment under inert atmosphere, highly pure and crystalline Cu2Mo6S8 could be obtained in only 400 s from this precursor, the Chevrel binary phase Mo6S8 was then obtained by copper removal through acidic leaching, and was evaluated as a positive electrode material for Mg-battery. The electrochemical performance in half-cell configuration shows reversible capacity exceeding 80 mAh/g, which is comparable to previous works carried out with materials synthesized by conventional high-temperature solid-state routes
Insight into the electrochemical behavior of micrometric Bi and Mg3Bi2 as high performance negative electrodes for Mg batteries
No full textThe electrochemical behavior of micrometric Bi powder as an active electrode material for Mg batteries is revisited in a half-cell with Mg metal as the counter electrode and organohaloaluminate-based complex electrolyte. A complete biphasic domain is evidenced from Bi to its Mg-alloyed counterpart Mg3Bi2. Operando X-ray diffraction underlines a simple mechanism that does not imply any intermediate phases or amorphization process. The high performances of Bi-based electrodes are confirmed using an optimized electrode formulation, with specific capacity nearing the theoretical value of 385 mA h g-1 at low rates. The capacity fading appears limited when moving to high current densities. In parallel, a micrometric Mg3Bi2 intermetallic compound obtained by high-energy ball-milling exhibits a similar electrochemical behavior. As a proof-of-concept as-prepared Mg3Bi2 is directly associated with a Chevrel-type positive electrode and successfully tested as a complete Mg-ion battery. Despite the high molar mass, the couple Bi/Mg3Bi2 can be considered as a reliable negative electrode candidate and a reference system for testing the next generation of Mg-ion battery electrolytes
Electrochemical magnesiation of the intermetallic InBi through conversion-alloying mechanism
No full textIntermetallic InBi has been prepared for the first time by high-energy mechanochemical synthesis from metallic In and Bi powders. Considering that both In and Bi are able to electrochemically alloy with Mg, InBi-based electrodes in Mg-battery were also investigated by operando X-ray diffraction in order to verify a possible synergy between the two metals in the reaction vs. Mg. In contrast to the relatively simple magnesiation mechanisms of both pure metals, the overall alloying mechanism of InBi - leading to the formation of Mg3Bi2 and MgIn - reveals an unexpected complex pathway through several successive intermediate phases, with InBi being reformed as a major product at the end of the charge. The presence of lone In during the reversible magnesiation process strongly affects the electrochemical properties. Indeed the cycling performance is intermediate between those of pure In- and Bi-based electrodes, without any beneficial synergy between the two active elements
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
First investigation of indium-based electrode in Mg battery
No full textMicrometric indium powder was investigated for the first time as active material for Mg battery negative electrodes using Mg-organohaloaluminate electrolyte. Indium electrochemically alloys with Mg to form the intermetallic compound MgIn. The alloying reaction is highly reversible. At low cycling rate, a high capacity of 425 mAh g- 1 is achieved, with the lowest alloying potential ever reported vs. Mg. The investigation of the electrochemical mechanism by operando x-ray diffraction confirmed a biphasic transition from In to MgIn in agreement with the Mg-In phase diagram, and without any intermediate amorphization process. High and stable capacity is observed by cycling at low rates, whereas rate-capability tests evidenced a rapid fading upon high current densities. Micrometric intermetallic MgIn directly synthesized by high-energy ball milling was also investigated and exhibited similar electrochemical behavior. These results confirm the interest of p-block elements as possible negative electrode materials for Mg batteries
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
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe 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
Electrochemical Mg alloying properties along the Sb1-xBix solid solution
No full textDespite strong physical and chemical similarities between antimony and bismuth, a distinct behaviour is observed in the electrochemical magnesiation of their micrometric powders. Bismuth undergoes a complete and highly reversible alloying reaction, whereas antimony displays no electrochemical activity. Taking advantage of the complete Sb[sbnd]Bi solid solution, monophasic compositions Sb1-xBix were prepared by high-energy mechanochemical synthesis and characterized by X-ray diffraction and solid-state 25Mg nuclear magnetic resonance spectroscopy. The electrochemical magnesiation at low current rate shows a full alloying process of Sb1-xBix-based electrodes leading to monophasic Mg3(Sb1-xBix)2. This chemical association of antimony and bismuth enables a positive effect on the electrochemical magnesiation of the electrode and enables higher specific capacities compared to Bi-based electrodes. However, this synergy only operates in the nominal discharge since an irreversible capacity loss, which scales with the antimony content, is observed in the subsequent charge. Operando XRD reveals a complex segregation process leading to pure bismuth and Mg3Sb2 at the end of charge which is further rationalized by density functional theory calculations as an instability of the Mg3(Sb1-xBix)2 solid solution
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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