1,721,016 research outputs found
Improved Electrochemical Performance of a LiFePO4-Based Composite Cathode
No full textLiFePO4 was synthesized in the presence of high-surface area carbon-black. The carbon was added to the precursors before the formation of the crystalline phase. SEM micrographs confirmed that the addition of the fine carbon powder reduces the LiFePO4 grain size. The carbon is uniformly dispersed between the grains, ensuring a good electronic contact. Electrochemical tests showed that the material obtained by adding 10 wt.% of carbon gives enhanced performance in terms of improved practical capacity and charge/discharge rate. The specific capacity was seen to increase on increasing temperatures. The full capacity (170 mA h g− 1) was delivered when discharging the cell at 80 °C and C/10 rate. The cyclability of the material was tested at room temperature and C/2 rate. The cell was cycled for over 230 cycles with an average specific capacity of about 95 mA h g− 1. © 2001 Elsevier Science Ltd. All rights reserved
A morfological study of SEI film on graphite electrodes.
No full textMorphological features of the protective layer on the graphitic electrodes, formed by reduction of electrolytic solution components during the ®rst cycle, are investigated by SEM and common electrochemical techniques. As expected, the interaction between electrode and solution is very important, leading to quite different results for different solutions. Here, results for solution of various solvents ratio are reported. It appears that the performances of the electrodes are strongly dependent on their surface chemistry in solutions. We can conclude that the nature of the surface ®lm plays a key role for the electrode stability or to capacity decrease always related to an increase of the electrode itself impedance. 5 2001 Elsevier Science B.V. All rights reserved
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
Functionalization of single-wall carbon nanotubes: a new promising nanomaterial for neurotransmitters detection.
No full textDetermination of Chemical Diffusion Coefficient of Lithium in LiFePO4
No full textThe lithium insertion in the ordered olivine-type structure of LiFePO4 was analyzed as an insertion process with a Frumkin- type sorption isotherm. A minimum in the chemical diffusion coefficient of lithium (DLi) was predicted by the model for strong attractive interactions between the intercalation species and the host matrix. The DLi in the material was measured as a function of the lithium content by using the galvanostatic intermittent titration technique (GITT). The diffusion coefficient was found 1.8 10 14 and 2.2 10 16 cm2 s 1 for LiFePO4 and FePO4, respectively, with a minimum in correspondence of the peak of the differential capacity. The DLi has also been measured by AC impedance method for various lithium contents. The calculated values are in very good agreement with the previous calculated ones. D 2002 Elsevier Science B.V. All rights reserved
Electrochemical characterization of glass/Al reactions at high temperature
No full textA high temperature Al(-)/glass/stainless steel-O2(+) system, was studied and characterized by SEM and EDS analysis. Indeed, a potential ranging from 1.75 to 1.5 V between steel and aluminum, at a temperature above 500 C, has been observed. By connecting this package to a resistance, a current flow was detected. Above the aluminum melting point, there is a reaction between SiO 2 glass and metal, with formation of Al2O3 and Si, moreover there is a change in the soda-lime glass composition, a nucleation of crystalline phases in the glass itself, and the formation of a porous layer of alumina, with the typical inhomogeneity of a system heated at this temperature. It seems that the current passing through the glass phase, by the electric field generated by the formation of a metal/air cell, can influence the composition of the glass phase at high temperature and can inhibit the nucleation and the growth of crystalline zones.A high temperature Al(−)/glass/stainless steel–O2(+) system, was studied and characterized by SEM and
EDS analysis. Indeed, a potential ranging from 1.75 to 1.5 V between steel and aluminum, at a temperature
above 500 °C, has been observed. By connecting this package to a resistance, a current flow was detected.
Above the aluminum melting point, there is a reaction between SiO2 glass and metal, with formation of
Al2O3 and Si, moreover there is a change in the soda-lime glass composition, a nucleation of crystalline phases
in the glass itself, and the formation of a porous layer of alumina, with the typical inhomogeneity of a system
heated at this temperature. It seems that the current passing through the glass phase, by the electric field
generated by the formation of a metal/air cell, can influence the composition of the glass phase at high temperature
and can inhibit the nucleation and the growth of crystalline zones
Study of the relationships between the structure of the doped spinels and their electrochemical performance in lithium batteries.
No full textDoping Li-Mn spinels with small amounts of metal ions (Zn, Ni, Co, Cr and Ti in this study) does remarkably affects its structural and electrochemical characteristics
- …
