1,720,969 research outputs found
–gC) composite through the hydrothermal process and its application as the anode of lithium ion batteries
No full textA mesostructured TiO2-graphitic carbon (TiO2-gC) composite was synthesized through a simple and scalable hydrothermal method to be employed as an anode material in Li-ion batteries. In a wide voltage range (0.0-2.5 V), the TiO2-gC composite anode possesses a high initial lithiation capacity (598 mA h g(-1)) at 0.1 C (1 C: 150 mA g(-1)), and it still retains 369 mA h g(-1) after 50 cycles at 0.5 C. Furthermore, under a high current density of 2 C, the TiO2-gC anode exhibits stable capacity (252 mA h g(-1)) retention for up to 200 cycles. This excellent electrochemical performance could be ascribed to a synergistic effect of well-developed mesoporosity with a high surface area (345.4 m(2) g(-1)), the conductive graphitic carbon wall, and uniformly dispersed TiO2 nanoparticles, resulting in improved Li+ penetration, fast electron transport and high structural stability during cycling.
Thermally Robust Porous Bimetallic (NixPt1-x) Alloy Mesocrystals within Carbon Framework: High-Performance Catalysts for Oxygen Reduction and Hydrogenation Reactions
No full textThermally stable porous bimetallic (NixPt1x) alloy mesocrystals within a carbon framework are produced via an aerosol-assisted process for high-performance catalysts for the oxygen reduction reaction (ORR) and hydrogenation. The porous NixPt1x alloy has a robust composite of alloy nanoparticles with an adjustable composition and a porous carbon skeleton. Porous Ni(x)Pt(1)x alloys exhibit high thermal stability, retaining their crystalline structure and morphology at 550 degrees C for 6 h, as observed in thermal treatment tests under various conditions (time, temperature, and atmosphere). The porous NixPt1x alloy as a catalyst for the hydrogenation of propylene has high conversion efficiency (>80%) and low activation energy (E-a < 20 kJ/mol) at >= 80 degrees C through the suitable control of the element composition and a pore structure. As a catalyst for the ORR, the catalytic activity of the porous NixPt1x alloy is superior to that of conventional Pt/C (0.115 mA) (0.853 mA/cm(Pt)(2) at 0.9 V/cm(Pt)(2)). This is attributed to the homogeneous alloying of the metal components (Ni and Pt) and the increased accessibility of the reactants to the catalyst, resulting from the unique morphology of the porous NixPt1x alloy, i.e., hierarchical structure with high porosity.
All-solid-state lithium-ion batteries with TiS2 nanosheets and sulphide solid electrolytes
No full textBulk-type all-solid-state lithium-ion batteries (ASLBs) using sulphide solid electrolytes (SEs) are considered as one of the promising alternative batteries because of their ultimate safety and scalable fabrication. However, they suffer from poor ionic contacts between active materials and SEs. Herein, we report, for the first time, the excellent electrochemical performances of sulphide-SE-based bulk-type ASLBs employing TiS2 nanosheets (TiS2-NSs) prepared by scalable mechanochemical lithiation, followed by exfoliation in water under ultrasonication. The TiS2-NS in all-solid-state cells exhibits an enhancement of reversible capacity which is attributed to the SE region in intimate contact with TiS2-NSs. Importantly, an exceptionally superior rate capability of the TiS2-NS compared to that of bulk TiS2 and even ball-milled TiS2, which is attributed to the ultrathin 2D structure (with short Li-ion diffusion length and intimate contacts between the TiS2-NS and SE) and high electronic conductivity, is highlighted.clos
Semimicro-size agglomerate structured silicon-carbon composite as an anode material for high performance lithium-ion batteries
No full textA semimicro-size agglomerate structured silicon-carbon (mSi-C) composite is constructed by an aggregation of silicon nanoparticles (similar to 100 nm) coated with conductive carbon layer through a facile and scalable aerosol-assisted process to be employed as an anode material for lithium-ion batteries (LIBs). As formed mSi-C composite delivers good electrochemical performances of high reversible capacity (2084 mAh/g) between 0.01 and 1.50 V (vs. Li/Li+) at 0.4 A/g, 96% capacity retention (1999 mAh/g) after 50 cycles and good rate capability (906 mAh/g) at 12 A/g. Such good performances can be attributed to 1) unique composite structure which accommodates the stress induced by volume change of silicon during lithiation/delithiation and facilitates ion transport, and 2) conformally formed carbon layer which enhances conductivity of the composite and helps to form a stable SEI layer. In addition, a high tap density (0.448 g/cm(3)) of mSi-C composite leads to high volumetric capacity (933 mAh/cm(3)), allowing its practical applications as an anode material towards high performance LIBs.clos
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
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
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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