1,720,963 research outputs found
Characterization of PVdF(HFP) gel electrolytes based on 1-(2-hydroxyethyl)-3-methyl imidazolium ionic liquids
No full textPoly(vinylidenefluoride)-hexafluoropropylene (PVdF(HFP)) -ionic liquid gel electrolytes were prepared using ionic liquids based on 1-(2-hydroxyethyl)-3-methyl imidazolium tetrafluoroborate and 1-(2-hydroxyethyl)3-methyl imidazolium hexafluorophosphate. A conventional metathesis reaction was used to prepare these ionic liquids, which have high purity and exhibit a liquid state at room temperature. The prepared polymerionic liquid gel proved to be a free-standing and rubbery film in which the degree of transparency differed according to the ratio and type of ionic liquid used. TGA and FTIR analyses confirmed that the solvent, N,N-Dimethylacetamide (DMAC), used for mixing PVdF(HFP) polymer with ionic liquid was almost totally removed during the gelling and drying processes. SEM photographs were taken of the surface structure of the PVdF(HFP)-ionic liquid gel in order to evaluate the morphology of the film's surface according to the mixing ratio and the nature of the ionic liquid. The thermal behaviors of PVdF(HFP)-ionic liquid gels were observed to be similar to those of neat ionic liquids through DSC analysis, and the compatibility between the polymer and ionic liquid was investigated by XRD analysis. The ionic conductivities of all the gels were 10(-3)-10(-5) S cm(-1) in a temperature range of 20-70 degrees C.This work was supported by Grant R01-2003-000-10300-0 from the Basic Research Program of the Korea Science & Engineering Foundation, and was partially funded by the Brain Korea 21 Project. The authors thank KBSI (Korea Basic Science Institute) for assistance with NMR, FAB mass, and ion chromatography, and Reliability Assessment Center of KRICT (Korea Research Institute of Chemical Technology) for assistance with DSC and TGA
N-Butyl-N-methylmorpholinium bis(trifluoromethanesulfonyl) imide-PVdF(HFP) gel electrolytes
No full textIonic liquid-polymer gels were prepared by incorporating N-butyl-N-methylmorpholinium bis(trifluoromethanesulfonyl)imide (Mor(1.4)TFSI) and poly(vinylidene fluoride)-hexafluoropropylene copolymer (PVdF(HFP)) using three different methods in order to observe the variation of ionic conductivities according to the presence of propylene carbonate (PC) and various weight ratios between Mor(1.4)TFSI and gel polymer electrolyte (GPE). Ionic conductivities for each gel polymer electrolyte were measured with increasing temperature. Ionic conductivities of the GPEs increased with increasing temperature and weight ratio of Mor(1.4)TFSI. In addition, the addition of PC into GPE led to the improvement of ionic conductivities. Thermogravimetric analysis (TGA) showed the suggested gel polymer electrolytes composed of only ionic liquid and polymer were stable up to approximately 400 degrees C. TGA and infrared spectroscopy data indicated that residual PC remains after evaporating PC in a vacuum oven, which did not affect the ionic conductivities. The GPEs containing PC displayed high conductivity (ca. 10(-2) S cm(-1)) at 60 degrees C. (C) 2005 Elsevier Ltd. All rights reserved
Facile one-pot synthesis of gold nanoparticles using alcohol ionic liquids
No full textWe developed a novel synthesis of Au nanoparticles using alcohol ionic liquids. The alcohol ionic liquids simultaneously serve as both reductants and protective agents, thereby significantly simplifying the process of nanoparticle preparation
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
Size-controlled electrochemical synthesis of palladium nanoparticles using morpholinium ionic liquid
No full textWe have successfully synthesized morpholinium ionic liquid-stabilized palladium (Pd) nanoparticles by electrochemical reduction. For characterization of Pd nanoparticles, FT-IR, UV-visible spectroscopy, and Transmission electron microscopy (TEM) were employed. The FT-IR spectrum of Pd nanoparticles indicated the surface binding of the IL to the nanoparticles. The UV-visible spectrum showed that nano-sized I'd particles were produced. The particle size was controlled by the adjustment of the current density, temperature, and electrolysis duration. The TEM images showed an average size of 2.0, 2.2, 2.4, 2.9, 3.5, 3.9, and 4.5 nm. Nearly a 0.5 run-sized control of the nanoparticle was achieved. The particle size increased with a decrease in the current density and an increase in temperature and electrolysis duration. The electron diffraction patterns of resulting nanoparticles indicated that the particles had a crystalline structure.This work was supported by Grant No. R01-2003-000-10300-0
from the Basic Research Program of the Korea Science & Engineering
Foundation and also partially funded by the Brain Korea
21 Project. We are grateful to KBSI (Korea Basic Science Institute)
for assistance with NMR, FAB mass, and ion chromatograph
Physical and electrochemical properties of 1-(2-hydroxyethyl)-3-methyl imidazolium and N-(2-hydroxyethyl)-N-methyl morpholinium ionic liquids
Full text linkVarious ionic liquids (ILs) were prepared via metathesis reaction from two kinds of 1-(2-hydroxyethyl)-3-methyl imidazolium ([HEMIm](+)) and N-(2-hydroxyethyl)-N-methyl morphorinium ([HEMMor](+)) cations and three kinds of tetrafluoroborate ([BF4](-)), bis(trifluoromethanesulfonyl)imide ([TFSI](-)) and hexafluorophosphate ([PF6](-)) anions. All the [HEMIm](+) derivatives were in a liquid state at room temperature. In particular, [HEMIm][BF4] and [HEMIm][TFSI] showed no possible melting point from -150 degrees C to 200 degrees C by DSC analysis, and their high thermal stability until 380-400 degrees C was verified by TGA analysis. Also, their stable electrochemical property (electrochemical window of more than 6.0 V) and high ionic conductivity (0.002-0.004 S cm(-1)) further confirm that the suggested ILs are potential electrolytes for use in electrochemical devices. Simultaneously, the [HEMMor](+) derivatives have practical value in electrolyte applications because of their easy synthesis procedures, cheap morpholinium cation sources and possibilities of high Li+ mobility by oxygen group in the morpholinium cation. However, [HEMMor](+) derivatives showing high viscosity usually had lower ionic conductivities than [HEMIm](+) derivatives. (C) 2005 Elsevier Ltd. All rights reserved.This work was supported by Korea Institute of Science and Technology (KIST) and also partially funded by the Brain Korea 21 Project. The authors would like to thank Korea Basic Science Institute (KBSI) for assistance with NMR, FAB mass and ion chromatography and Reliability Assessment Center of Korea Research Institute of Chemical Technology (KRICT) for assistance with DSC and TGA
Thermal and electrochemical properties of morpholinium salts with bromide anion
No full textThe present work is a study of the thermal properties and electrochemical stabilities of N-ethyl-N-methyl-morpholinium bromide ([Mor(1.2)][Br]), N-butyl-N-methylmorpholinium bromide ([Mor(1.4)][Br]), N-butyl-N-methylmorpholinium bromide ([Mor(1.8])[Br]), N-dodecyl-N-methylmorpholinium bromide ([Mor(1,12)] [Br]), and N,N-dihydroxyethylmorpholinium bromide ([DHEMor][Br]). The melting points, decomposition temperatures, and electrochemical stabilities of the salts were measured by DSC (differential scanning calorimetry), TGA (thermogravimetric analysis), and CV (cyclic voltammogram), respectively. All salts were decomposed below approximately 230.00 degrees C and their melting points were above 100.00 degrees C except [DHEMor][Br], which melted at 75.17 degrees C. [DHEMor][Br] appeared to possess the most wide liquid-phase range between melting point and decomposition temperature. The electrochemical windows of salts ranged from 3.3 V for [Mor(1)(8)(.)][Br] to 3.6 V for [Mor(1.4)][Br] and thus did not show any noticeable variation with cations used for salt synthesis
Carbide-derived-carbons with hierarchical porosity from a preceramic polymer
No full textSynthesis of carbon by extraction of metals from carbides has been successfully used to
produce a variety of micro-porous carbide-derived carbons (CDCs) with narrow pore size
distributions and tunable sorption properties. This approach is of limited use when larger
mesopores are targeted, however, because the relevant synthesis conditions yield broad
pore size distributions. Here we demonstrate the porosity control in the 3–10 nm range
by employing preceramic polymer-derived silicon carbonitride (SiCN) precursors. Polymer
pyrolysis in the temperature range 600–1400 C prior to chlorine etching yields disordered
or graphitic CDC materials with surface area in the range 800–2400 m2 g1. In the hierarchical
pore structure formed by etching SiCN ceramics, the mesopores originate from etching
silicon nitride (Si3N4) nano-sized crystals or amorphous Si–N domains, while the micropores
come from SiC domains. The etching of polymer-derived ceramics allows synthesis
of porous materials with a very high specific surface area and a large volume of mesopores
with well controlled size, which are suitable for applications as sorbents for proteins or
large drug molecules, and supports for metal catalyst nanoparticles
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
- …
