1,720,959 research outputs found
Fabrication and electrochemical characterization of LiCoO2 cathode powder by mechanochemical process
No full textLiCoO2 cathode powders with a grain size of 1-1.5 mum were synthesized by a mechanochemical process. The Li-Co precursor was prepared by a freeze drying method using a Li and Co acetate as starting raw materials. The surface was modified by lapping the precursor using K2SO4 in a simple ballmill. After the surface modification, the Li-Co precursor was heated at 800degreesC to form a high-temperature polymorph. The K2SO4 coat on the Li-Co precursor prevented the Li-Co precursors from contacting one another, due to the high decomposition temperature of K2SO4 above 1000degreesC and constrains grain growth. Because of this, the modified Li-Co precursor is converted to very small crystalline LiCoO2 particles by phase transformation. The as-synthesized LiCoO2 powder had well-developed facets and a very uniform grain size distribution. A small capacity fade for high discharge rate was observed in the as-synthesized powder, which can be attributed to the diffusion of Li ions at the grain boundary. Thus, it is possible not only to synthesis LiCoO2 powder to a desired grain size but also to control the grain size distribution using this method. These results indicated that the synthesis of a high-temperature polymorph of LiCoO2 with a small grain size is possible by constraining growth during the heat-treatment. The LiCoO2 powder synthesized here represents a very good candidate for use in fabricating not only of high power bulk batteries but high power slim batteries as well, when a thin and thick film process is used. (C) 2004 The Electrochemical Society.National Research Laboratory program (development of monolithic high performance battery
Preparation and electrochemical characterization of size controlled SnO2-RuO2 composite powder for monolithic hybrid battery
No full textTin oxide (SnO2) powders with a particle size of similar to20 nm were synthesized by a gas condensation method. Ruthenium oxide was loaded by an incipient-wetness method, in which an aqueous solution of RuCl3 was added to the manufactured SnO2 powder in an amount that was just sufficient to wet completely the powder. And then, the resulting solution was obtained after freeze-drying to synthesis the smallest particle. The as-synthesized SnO2 powder with 1.5 wt.% ruthenium oxide (RuO2) exhibited well-developed facets and had a very uniform particle size. The first discharge capacity was lower than comparing to commercial powder because of forming the second phase, but showed good cyclability. A maximum specific electrode capacitance of similar to20 F/g and a maximum specific power of similar to80 W/kg were achieved by manufactured SnO2 With 1.5 wt.% RuO2. This result indicated that the synthesized SnO2-RuO2 composite powder of nano-size scale is candidate for use in fabricating monolithic hybrid batteries using suitable electrolyte as well. (C) 2004 Elsevier Ltd. All rights reserved.R&D supporting by National ResearchL aboratory program (Development of monolithic
high power hybrid batter
Theoretical calculation of near-edge x-ray-absorption fine structure of LiMO2 cathode materials using model clusters
No full textCharacteristics of ZnO thin film deposited on various metal bottom electrodes
No full textZnO films for electronic applications were deposited by radio-frequency (rf) sputtering onto various metal bottom electrodes (Pt/Ti, W Ni) to investigate such structural properties as crystallinity and surface morphology. The crystallinity, surface morphology and composition of the as-deposited films were studied using X-ray diffraction (XRD), scanning electron microscopy (SEM) and Rutherford back-scattering spectrometry (RBS), respectively. The preferred orientation and surface morphologies were strongly influenced by the type of bottom electrodes. The ZnO films with (200) texturing deposited on Pt/Ti/SiO2/Si showed a smoother and smaller grain size than those deposited on W and Ni. The ZnO films on Pt and W electrodes exhibited compressive residual stress
Theoretical calculation of electronic structure and X-ray absorption near-edge structure of cathode materials for Li ion batteries
No full textFirst principles calculations were performed on the electronic structure, chemical bonding and X-ray absorption near edge structure (XANES) of various lithium transition metal oxides. In the electronic structure using the discrete variational X alpha method (DV-X alpha), chemical bonding is changed by Li deintercalation. Li is found to be nearly ionized in LiMO2 and strong covalent bonding between M and O is noted. The larger the difference of covalency between cation and nearest neighbor anion when Li intercalated/deintercalated is, the lower the voltage calculated by Vienna Ab Initio Simulation Package (VASP) is. By calculations of transition state, we reproduce the characteristics of the spectra as well as the chemical shifts and the origin of peaks appearing in the experimental XANES spectra is interpreted in terms of orbital interactions using bond overlap population diagrams. (c) 2006 Elsevier B.V. All rights reserved.Ministry of Education(“Brain Korea 21”) and the Ministry of Science and Technology. Experiments at PLS were supported in part by
MOST and POSTECH. Special thanks to Prof. Isao Tanaka at Kyoto University for supporting the VASP
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
Orientation and fatigue improvement of PZT thin films on cubic textured CaRuO3 electrode
No full textIn this study, we report on the (100) cube-textured Pb(Zr 0.4 ,Ti 0.6 )O 3 (PZT) thin films using a conducting perovskite CaRuO 3 (CRO) bottom electrode, and which was compared to the (111) textured PZT on Pt electrode. X-ray diffraction (XRD) reveals that the CRO bottom electrode has a pseudo-cubic nature on Si, and the PZT thin films prepared on CRO/Si shows a (100) textured growth. PZT films on CRO electrode have a well-saturated ferroelectricity with a remanent polarization (P r ) and coercive field (E c ) of 25 mu C/cm 2 and 75 kV/cm, respectively. These PZT films are more fatigue resistive character than that on Pt bottom electrode.Ministry of Education (project named “Brain Korea 21”).
Dr.Seung-Hyun Kim, in Inostek Inc., Korea, and Heesan Kim, Ph.D. candidate the
Department of Material Science & Engineering, KAIST, Korea
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
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