Room Temperature Ionic Liquid-Lithium Salt Mixtures: Optical Kerr Effect Dynamical Measurements

The addition of lithium salts to ionic liquids causes an increase in viscosity and a decrease in ionic mobility that hinders their possible application as an alternative solvent in lithium ion batteries. Optically heterodyne-detected optical Kerr effect spectroscopy was used to study the change in dynamics, principally orientational relaxation, caused by the addition of lithium bis(trifluoromethylsulfonyl)imide to the ionic liquid 1-buty1-3-methylimidazolium bis(trifluoromethylsulfonyl)imide. Over the time scales studied (1 ps-16 ns) for the pure ionic liquid, two temperature-independent power laws were observed: the intermediate power law (1 ps to similar to 1 ns), followed by the von Schweidler power law. The von Schweidler power law is followed by the final complete exponential relaxation, which is highly sensitive to temperature. The lithium salt concentration, however, was found to affect both power laws, and a discontinuity could be found in the trend observed for the intermediate power law when the concentration (mole fraction) of lithium salt is close to chi(LiTf(2)N) = 0.2. A mode coupling theory (MCT) schematic model was also used to fit the data for both the pure ionic liquid and the different salt concentration mixtures. It was found that dynamics in both types of liquids are described very well by MCT.

Intralamellar structural modifications related to the proton exchanging in K(4)Nb(6)O(17) layered phase

Basic structural aspects about the layered hexaniobate of K(4)Nb(6)O(17) composition and its proton-exchanged form were investigated mainly by spectroscopic techniques. Raman spectra of hydrous K(4)Nb(6)O(17) and H(2)K(2)Nb(6)O(17)center dot H(2)O show significant modifications in the 950-800 cm(-1) region (Nb-O stretching mode of highly distorted NbO(6) octahedra). The band at 900 cm(-1) shifts to 940 cm(-1) after the replacement of K(+) ion by proton. Raman spectra of the original materials and the related deuterated samples are similar suggesting that no isotopic effect occurs. Major modifications were observed when H(2)K(2)Nb(6)O(17) was dehydrated: the relative intensity of the band at 940 cm(-1) decreases and new bands seems to be present at about 860-890 cm(-1). The H(+) ions should be shielded by the hydration sphere what preclude the interaction with the layers. Removing the water molecules, H(+) ions can establish a strong interaction with oxygen atoms, decreasing the bond order of Nb-O linkage. X-ray absorption near edge structure studies performed at Nb K-edge indicate that the niobium coordination number and oxidation state remain identical after the replacement of potassium by proton. From the refinement of the fine structure, it appears that the Nb-Nb coordination shell is divided into two main contributions of about 0.33 and 0.39 nm, and interestingly the population, i.e., the number of backscattering atoms is inversed between the two hexaniobate materials. 2009 Elsevier Ltd. All rights reserved.

Identification of lift-off mechanism failure for salt drill-in drilling fluid containing polymer filter cake through adsorption/desorption studies

Drilling fluid`s contact with the productive zone of horizontal or complex wells can reduce well productivity by fluid invasion in the borehole wall. Salted drilling drill-in fluid containing polymers has often been applied in horizontal or complex petroleum wells in the poorly consolidated sandstone reservoirs of the Campos basin, Rio de Janeiro, Brazil. This fluid usually consists of natural polymers such as starch and xanthan gum, which are deposited as a filter cake on the wellbore wall during the drilling. Therefore, the identification of a lift-off mechanism failure, which can be detachment or blistering and pinholing, will enable formulation improvements. increasing the chances of success during filter cake removal in open hole operations. Likewise, knowledge of drill-in drilling fluid adsorption/desorption onto sand can help understand the filter cake-rock adhesion mechanism and consequently filter cake lift-off mechanism failures. The present study aimed to identify the lift-off failure mechanism for this type of fluid filter cake studying adsorption/desorption onto SiO(2) using solutions of natural polymers, lubricants, besides the fluid itself. Ellipsometry was employed to measure this process. The adsorption/desorption studies showed that the adsorbed layer of drilling fluid onto the walls of the rock pores is made up of clusters of polymers, linked by hydrogen bonds, which results in a force of lower cohesion compared to the electrostatic interaction between silica and polymers. Consequently, it was found that the most probable filter cake failure mechanism is rupture (blistering and pinholing), which results in the formation of ducts within the filter cake. (C) 2009 Elsevier B.V. All rights reserved.

Picosecond Dynamics of Proton Transfer of a 7-Hydroxyflavylium Salt in Aqueous-Organic Solvent Mixtures

The intermediacy of the geminate base proton pair (A*center dot center dot center dot H(+)) in excited-state proton-transfer (ESPT) reactions (two-step mechanism) has been investigated employing the synthetic flavylium salt 7-hydroxy-4-methyl-flavylium chloride (HMF). In aqueous solution, the ESPT mechanism involves solely the excited acid AH* and base A* forms of HMF as indicated by the fluorescence spectra and double-exponential fluorescence decays (two species, two decay times). However, upon addition of either 1,4-dioxane or 1,2-propylene glycol, the decays become triple-exponential with a term consistent with the presence of the geminate base proton pair A*center dot center dot center dot H(+). The geminate pair becomes detectable because of the increase in the recombination rate constant, k(rec), of (A*center dot center dot center dot H(+)) with increasing the mole fraction of added organic cosolvent. Because the two-step ESPT mechanism splits the intrinsic prototropic reaction rates (deprotonation of AH(+)*, k(d), and recombination, k(rec) of A*center dot center dot center dot H(+)) from the diffusion controlled rates (dissociation, k(diss) and formation, k(diff)[H(+)], of A*center dot center dot center dot H+), the experimental detection of the geminate pair provides a wealth of information on the proton-transfer reaction (k(d) and k(rec)) as well as on proton diffusion/migration (k(diss) and k(diff)).

Nickel hydroxide electrodes as amperometric detectors for carbohydrates in flow injection analysis and liquid chromatography

The present paper describes the utilization of nickel hydroxide modified electrodes toward the catalytic oxidation of carbohydrates (glucose, fructose, lactose and sucrose) and their utilization as electrochemical sensor. The modified electrodes were employed as a detector in flow injection analysis for individual carbohydrate detection, and to an ionic column chromatography system for multi-analyte samples aiming a prior separation step. Kinetic studies were performed on a rotating disk electrode (RDE) in order to determine both the heterogeneous rate constant and number of electrons transferred for each carbohydrate. Many advantages were found for the proposed system including fast and easy handling of the electrode modification, low cost procedure, a wide range of linearity (0.5-50 ppm), low detection limits (ppb level) and high sensitivities. (C) 2009 Elsevier B.V. All rights reserved.

Synthesis and characterization of stable Co and Cd doped nickel hydroxide nanoparticles for electrochemical applications

The present paper describes the physical-chemical characterization and electrochemical behavior of a new nanomaterial formed by the addition of cadmium and cobalt atoms into the structure of nickel hydroxide nanoparticles, these ones synthesized by an easy sonochemical method. Particles of about 5 nm diameter were obtained and characterized by high resolution transmission electron microscopy (HRTEM), X-ray diffraction and Raman spectroscopy. Different nickel hydroxide nanoparticles were immobilized onto transparent conducting substrates by using electrostatic layer-by-layer providing thin films at the nanoscale and the electrochemical behavior was investigated. The formation of a mixed hydroxide was corroborated by observation of very interesting properties as redox potential shifting to less positive potentials and high stability when submitted to long electrochemical cycling or high times of ultrasonic synthesis, suggesting practical applications. (C) 2008 Elsevier B.V. All rights reserved.

Electrochemical oxidation of glycine by doped nickel hydroxide modified electrode

The electrocatalytic oxidation of glycine by doped nickel hydroxide modified electrodes and their use as sensors are described. The electrode modification was carried out by a simple electrochemical coprecipitation and its electrochemical properties were investigated. The modified electrode presented activity for glycine oxidation after applying a potential required to form NiOOH (similar to 0.45 V vs Ag/AgCl). In these conditions a sensitivity of 0.92 mu A mmol(-1) L and a linear response range from 0.1 up to 1.2 mmol L(-1) were achieved in the electrolytic Solutions at PH 12.6. Limits of detection and quantification were found to be 30 and 110 mu mol L(-1), respectively. Kinetic studies performed with rotating disk electrode (RDE) and by chronoamperometry allowed to determine the heterogeneous rate constant of 4.3 x 10(2) mol(-1) Ls(-1), Suggesting that NiOOH is a good electrocatalyst for glycine oxidation. NiOOH activity to oxidize other amino acids was also investigated, (c) 2008 Elsevier B.V. All rights reserved.

Electrocatalytic oxidation of urea by nanostructured nickel/cobalt hydroxide electrodes

The present paper describes the catalytic oxidation of urea performed by nickel hydroxide and nickel/cobalt hydroxide modified electrodes by using both electrodeposited films and nanoparticles. The incorporation of Co foreign atoms leads to a slight increase in sensitivity besides the shift in redox process, avoiding the oxygen reaction. Nanostructured Ni80Co20(OH)(2) was synthesized by sonochemical route producing 5 nm diameter particles characterized by high-resolution transmission electron microscopy (HRTEM) being immobilized onto electrode by using the electrostatic Layer-by-layer technique, yielding attractive modified electrodes for sensor development. (C) 2007 Elsevier Ltd. All rights reserved.

Transport coefficients, Raman spectroscopy, and computer simulation of lithium salt solutions in an ionic liquid

Lithium salt solutions of Li(CF3SO2)(2)N, LiTFSI, in a room-temperature ionic liquid (RTIL), 1-butyl-2,3-dimethyl-imidazolium cation, BMMI, and the (CF3SO2)(2)N-, bis(trifluoromethanesulfonyl)imide anion, [BMMI][TFSI], were prepared in different concentrations. Thermal properties, density, viscosity, ionic conductivity, and self-diffusion coefficients were determined at different temperatures for pure [BMMI][TFSI] and the lithium solutions. Raman spectroscopy measurements and computer simulations were also carried out in order to understand the microscopic origin of the observed changes in transport coefficients. Slopes of Walden plots for conductivity and fluidity, and the ratio between the actual conductivity and the Nernst-Einstein estimate for conductivity, decrease with increasing LiTFSI content. All of these studies indicated the formation of aggregates of different chemical nature, as it is corroborated by the Raman spectra. In addition, molecular dynamics (MD) simulations showed that the coordination of Li+ by oxygen atoms of TFSI anions changes with Li+ concentration producing a remarkable change of the RTIL structure with a concomitant reduction of diffusion coefficients of all species in the solutions.

A New Insight on the Preparation of Stabilized Alpha-Nickel Hydroxide Nanoparticles

Nickel hydroxide can provide an outstanding cathode material in alkaline secondary batteries, however the progressive decrease of the charge capacity as a function of the number of oxidation/reduction cycles is a challenging problem to be solved. New improvements on the electrochemical properties of electrode materials can be achieved by exploiting the much better performance of alpha-nickel hydroxide. Such materials were obtained in a stable form by sol-gel method and characterized by thermogravimetric analyses, UV-Vis spectroscopy, X-ray diffractometry, scanning and transmission electron microscopy, cyclic voltammetry and electrochemical quartz crystal microbalance techniques. The results revealed not only the formation of the alpha-Ni(OH)(2) phase, but also a much better electrochemical reversibility and stability as compared with similar materials obtained by electrochemical precipitation method.

Influence of hardwood, softwoodand fractionated pulp in a stratifiedthree-layered fine paper : Lövved, barrved och fraktionerad massa ochdess inverkan på ett treskiktat finpapper

Four different trials of stratified three-layered fine paper, of sulphate pulp, were performed to investigate if stratified fine fraction or fibres from birch can improve the properties of a paper compared to a reference sheet. All trials had five different scenarios and each scenario was calendered with different linear load. All sheets had a grammage of 80 g/m2.In the first trial, the paper contained birch, pine and filler of calciumcarbonate (marble), and was manufactured with the pilot paper machine XPM and the stratified headbox Formator at RCF (Stora Enso Research Center in Falun). The furnish consisted of 75% birch and 25% pine.The second trial contained coated sheets with paper from trial one as the base paper. The coating slip contained calciumcarbonate and clay and the amount was approximately 10-12 g/m2.The third trial, also with birch and pine but without filler, was performed at STFI (Skogsindustrins Tekniska Forskningsinstitut in Stockholm) with the laboratory scaled paper machine StratEx and the stratified headbox AQ-vanes. The furnish consisted of 75% birch and 25% pine, except for one scenario which contained of 75% pine and 25% birch.The last trial contained fractionated pulp of birch and pine and was performed at STFI. 50% was fine fraction and 50% was coarse fraction.This test does not show any clear benefits of making stratified sheets of birch and pine when it comes to properties such as bending stiffness, tensile index and surface smoothness. The retention can be improved with birch in the surface plies. It is possible that the formation can be improved with birch in the surface plies and pine in the middle ply. It is also possible that fine fraction in the surface plies and coarse fraction in the middle ply can improve both surface smoothness and bending stiffness. The results in this test are shown with confidence intervals which points out the difficulties of analysing sheets manufactured with a pilot paper machine or a laboratory scaled paper machine.

Share bidding auctions, sliding scale royalty rates and the new brazilian regulatory framework for the pre-salt areas

O governo brasileiro recentemente aprovou uma legislação instituindo um novo marco regulatório para as reservas petrolíferas do pré-sal. Segundo as novas regras, estas áreas deverão ser licitadas mediante um leilão de partilha de lucro. Motivado por esta mudança, apresentamos um modelo de leilão de partilha sob afiliação, demonstrando a existência de um equilíbrio monótono em estratégias puras e caracterizando a solução. Alem disso, provamos que este mecanismo gera receita esperada maior ou igual a um leilão de primeiro preço usual. Em seguida, introduzimos no modelo uma função representando taxas de royalties que dependem do valor do objeto. Este instrumento permite uma elevação na receita esperada de ambos os modelos, fazendo com que a diferença entre eles encolha. Finalmente, analisando o novo marco regulatório sob o ponto de vista dos resultados obtidos, concluímos que o antigo modelo de concessão utilizado pelo governo brasileiro é mais adequado e lucrativo.

Salt as a stress response mitigator of matrinxa, Brycon cephalus (Gunther), during transport

The present study evaluated the physiological responses of matrinxa, Brycon cephalus (Gunther), submitted to transport stress under the influence of sodium chloride, Different salt concentrations (0.0%, 0.1%, 0.3% and 0.6%) were added to four 200-L plastic tanks. Each tank was stocked with 30 fish (mean weight 1.0 +/- 0.2 kg) and transported for 4 h. Blood was sampled prior to transport and immediately after and 24 and 96 h after transport. Plasma cortisol and glucose and serum sodium and potassium, plasma chloride and ammonia were analysed, Changes in plasma cortisol were observed immediately after transportation, except in fish transported in 0.3% and 0.6% salt. Twenty-four hours later, this hormone had returned to its initial level in all fish. Blood glucose was not changed in fish treated with 0.6% salt immediately after transport, and returned to the initial level within 96 h after the other treatments. All treatments resulted in lower levels of plasma chloride after transport, except for fish treated with 0.6% salt, with fish treated with 0.0% and 0.3% salt recovering 24 h later, Serum sodium decreased immediately after transport only in the control fish, returning to the initial level 24 h later, the results indicate that treatment with 0.6% NaCl reduces most of the physiological responses of matrinxa to the stress of transport.