The electrochemical characteristics of sulfurized polyacrylonitrile composite (PAN/S) cathodes were compared with the commonly used carbon/S-based composite material. The difference in the working mechanism of these composites was examined. Analytical investigations were performed on both kinds of cathode electrode composites by using two reliable analytical techniques, in-situ UV-Visible spectroscopy and a four-electrode Swagelok cell. This study differentiates the working mechanisms of PAN/S composites from conventional elemental sulphur/carbon composite and also sheds light on factors that could be responsible for capacity fading in the case of PAN/S composites.

The subject of this paper is the extent to which, during wetting-drying cycles, chloride ions penetrate into fly ash modified concrete. Detailed chloride profiles were recorded which show how the total and water-soluble chloride contents vary with the depth of penetration of these ions into the concrete. In order to study the effect of exposure time, fly ash content, and fly ash composition on such penetration, two different types of fly ash were used as a partial replacement of Portland cement, their proportions amounting to 0%, 20% and 50% by weight of the binder.The results of the investigation showed that the chloride penetration depths were smaller in the case of the fly ash modified concretes than in the case of the unmodified concrete (i.e. concrete which did not contain fly ash), so that thinner layers of concrete cover could in this case be used to protect the steel reinforcement from the effects of corrosion. This indicates the potential beneficial effect of the use of fly ash on the service life of reinforced concrete structures. It is not just the porosity of the fly ash which plays a key role in the case of chloride penetration into concrete, but also the composition of the fly ash, and especially its calcium content. (C) 2015 Elsevier Ltd. All rights reserved.

This paper investigates the process of non-expansive alkali-carbonate reaction (ACR) in mortar prepared with dolomite aggregate with specific regard to the compressive strength increase of the mortar. Progress of ACR was studied for one year using the HIROX optical microscope system, a petrographic microscope, and scanning electron microscopy with X-ray microanalysis (SEM/EDS) at different simulated real and accelerated conditions. As reference a mortar mixture prepared by inert limestone aggregate was used. Compressive and flexural tests were also carried out parallel to the microscopic investigation, after 0, 3 and 6months of exposure to the above conditions. The results indicate that a considerably higher increase in compressive strength was detected over time for the mortar with dolomite aggregate, compared to the one with limestone aggregate. This can be correlated with time and exposure condition and attributed to alterations to the mortar due to ACR. Better interlocking between the Portland cement binder and the aggregate grains, due to formation of a new Mg–Si–Al phase, and a denser binder along the dedolomitised grains, due to formation of secondary calcite, are isolated as important reasons for the increase in compressive strength.

The active pharmaceutical ingredient orlistat is usually manufactured using a semi-synthetic procedure, producing crude product and complex mixtures of highly related impurities with minimal side-chain structure variability. It is therefore crucial for the overall success of industrial/pharmaceutical application to develop an effective purification process. In this communication, we present the newly developed water-in-oil reversed micelles and microemulsion system-based crystallization process. Physiochemical properties of the presented crystallization media were varied through surfactants and water composition, and the impact on efficiency was measured through final variation of these two parameters. Using precisely defined properties of the dispersed water phase in crystallization media, a highly efficient separation process in terms of selectivity and yield was developed. Small-angle X-ray scattering, high-performance liquid chromatography, mass spectrometry, and scanning electron microscopy were used to monitor and analyze the separation processes and orlistat products obtained. Typical process characteristics, especially selectivity and yield in regard to reference examples, were compared and discussed.

Some carbonate aggregates used in concrete are unstable in a high alkaline solution, which is present also in pore solution of cement binder. This paper investigates the process of dedolomitization of carbonate aggregate rocks and mortar bars. Selected aggregates, limestone and dolostone are of high purity without reactive silica involvement confirmed by the XRD and the XRF. For the process of dedolomitization the effect of various temperatures, solutions and time was examined. In this investigation, measurements of expansion, optical and scanning electron microscopy (SEM), energy dispersive spectrometry (EDS) and X-ray diffraction were used. Te results indicate that the process of dedolomitization occurred not only in the NaOH solution but also in the water on the mortar bar with virgin dolostone aggregate. Elevated temperature, 60 °C, increased the rate of reaction. Furthermore, the rate of reaction significantly correlates with time, which has also been confirmed through the Rietveld analysis.

X-ray single crystal diffraction data were used for structural refinement of the title compounds with different x (0.15, 0.27, 0.49, and 0.89). Crystals were grown in alumina crucibles using the self-flux method. Aluminum, which originates from the crucibles, substitutes only Cu(1), and thus induces tetragonal symmetry which was observed in all four crystals. The main structural effect of praseodymium is an increased separation of superconducting layers. Substituent concentrations (x and y in the formula) have been refined and compared with the values obtained by EDX (energy dispersive x-ray analysis) in an electron microscope. It was indicated that the refined values of Y: Pr ratio and the oxygen content are more reliable than those obtained by EDX while the refinement is less sensitive for Cu(1): Al ratio, and this value is more uncertain. This is in accordance with the result of wet chemical analysis.

The unique properties of reverse micelles, microemulsions, enable a variety of applications, from oil recovery to pharmaceuticals. For an effective process development for a targeted application, systems with specific ionic and molecular transport properties are needed. In this work, experiments were carried out to study microstructures of mixed reverse micelles, microemulsions (water/n-heptane), obtained with the use of anionic surfactants, sodium bis(2-ethylhexyl) sulfosuccinate (AOT) and the structural-related sodium bis(amyl) sulfosuccinate (DAS). Viscosity measurements, electrical conductivity, differential scanning calorimetry (DSC) and small-angle X-ray scattering (SAXS) were experimental techniques used for characterization of the prepared systems. The effect of DAS content on conductivity was that with increasing molar ratio of DAS/AOT (concentration of Na+ cations was kept at constant) the conductivity maximum shifted to lower water content, indicating an enlargement in reverse micelles size, which was also confirmed by SAXS analysis. It was further observed that at total surfactant concentrations of 0.45 mol/L, at a DAS/AOT molar ratio of 10/90, and 0.35 mol/L, at a DAS/AOT molar ratio of 15/85, this maximum almost vanished but an additional conductivity maximum at the composition with higher water content was detected. The effect of DAS on percolation phenomena was striking. The percolation threshold shifted towards smaller water content intensively with an increasing molar ratio of DAS/AOT and DAS concentration to an extent that the conductivity maximum overlapped with the percolation peak. The observed effect and a complementary viscosity and DSC analysis suggested clustering of mixed droplets in the low-water region. It has been confirmed that DAS enables formation of different aggregation states by influencing the rigidity of the oil/water interface in water/AOT-DAS/n-heptane mixed reverse micelles, w/o microemulsions. Our results have shown that by controlling DAS and water content it is possible to extensively modify the microstructure properties of the water/AOT-DAS/n-heptane system.

We report on the structure and electronic properties of single wall carbon nanotubes (SWNTs) tips with atomically spatial resolution. Scanning tunneling microscopy (STM) show topographic images of closed tips with a variety of geometrical structure; these include round, conical, as well as tips with a messy shape. At low bias voltage, topographic STM images show standing wave pattern of the charge density in the vicinity of nanotube ends. The patterns originate from constructive interference between the electronic states and its reflection on the nanotube tips. The modulations extend along 6-8 nm away from the cap. Atomically resolved images show asymmetry in the charge density that smears out as the bias voltage increases. These distinctive tip states do not exist elsewhere on the tube and are related to the presence of topological defects at tube ends.

Cathode degradation and methods for improving the selectivity of anode catalysts remain crucial challenges for the design of polymer electrolyte membrane fuel cells. A chemically modified Pt electrode with a self-assembled monolayer of calix[4]arene molecules is now shown to selectively block the undesired oxygen reduction reaction.

In the literature, the interpretation of electrochemical impedance spectra measured on insertion cathode materials is far from being unique. In most cases, various arbitrarily selected equivalent circuits have been used for analysis of spectra whereby the criterion of merit has mainly been the quality of fit. Herein, we propose a different approach. We try to explain the main features such as the high and medium frequency arcs and the low frequency diffusional tail using convenient (simplified) equivalent circuits derived from a quite general description of impedance due to a particulate (porous) system. The proposed models have a clear physical background. The meaning of selected circuit parameters is experimentally verified using carefully modeled experiments on LiFePO(4) and LiCoO(2) materials. In particular, we discuss the effects of state of charge, external pressure, electrode mass (thickness), and electrolyte concentration on the measured and simulated equivalent circuits. In the last part, we discuss in certain depth the complications arising from poor electronic or ionic contacting (wiring) between different phases constituting electrodes. (C) 2010 The Electrochemical Society. [DOI: 10.1149/1.3489353] All rights reserved.

Layered ZnO microspheric particles were prepared by the thermal decomposition of layered hydrozincite (LZnHC), which was synthesized from zinc nitrate and urea in a water/PEG400 mixture. The influence of the starting reagents, their concentrations, and the amount of PEG in the water/PEG400 mixture on the particle growth was observed. The chemical aspect of the particle growth was proposed in the frame of the partial charge model (PCM), and the formation of [Zn(OH)(2)(OH(2))(4)](0) and [Zn(OH)(HCO(3))(OH(2))(3)](0) was predicted for the solid phase. The assumed growth mechanism, which follows the "nonclassical crystallization" concept of a self-assembling mechanism, was observed in situ by small-angle X-ray scattering (SAXS) and predicts the rapid formation of approximately 6 nm sized building units. The size of these nano building units, stable only in the reaction medium, remains nearly constant during the synthesis, as the concentration of the nano building units increases throughout the reaction. The nano building units connect into leaves of LZnHC with a thickness of 20 nm. These leaves of LZnHC are further agglomerated into porous, microsphere-like particles with sizes up to 4 μm.

To enhance the high-rate capability (up to 120 C, 20 A/g) of nanoparticulate TiO2 (anatase) formed by thermal treatment of protonated TiO2 nanotubes, we used two types of additives: RuO2 as an electron-conductive material [Y.-G. Guo, Y.-S. Hu, W. Sigle, J. Maier, Adv. Mater. 19 (2007) 2087] and silica as a suppressant of particle growth during heat treatment. We show systematically that both additives, when used separately, improve the high-rate performance of anatase by 25–55 mA h/g at 60 C. The combined use of both additives in a total amount of merely 2.5 wt.% leads to an improvement of more than 70 mA h/g at 60 C. The underlying mechanisms for these significant effects are briefly discussed.

Binders in battery electrodes not only provide mechanical cohesiveness during battery operation but can also affect the electrode properties via the surface modification. Using atomic force microscopy (AFM), we study the surface structuring of three binders: polyvinylidene fluoride (PVdF), carboxymethyl cellulose (CMC) and gelatin. We try to find correlation between the observed structures and the measured electrochemical charge–discharge characteristics. We further measure the binding ability of gelatin adsorbed from solutions of different pHs. While the best binding ability of gelatin is obtained at pH about 9, the least polarization is observed at pH 12. Both properties are explained based on the observed gelatin structuring as a function of pH. In the second part of this study, gelatin is used as a surface agent that dictates the organization of nanometre-sized carbon black particles around micrometre-sized cathodic active particles. Using microcontact impedance measurements on polished pellets we show that using gelatin-forced carbon black deposition the average electronic resistance around LiMn2O4 particles is decreased by more than two orders of magnitude. We believe that it is this decrease in resistance that improves significantly the rate performance of various cathode materials, such as LiMn2O4 and LiCoO2.

Nanowire‐type materials produced by single‐step synthesis were investigated by XPS and HR AES. A sufficient quantity of these materials was produced for the XPS analyses. AES analyses at selected spots or along selected lines on the surface of the bundles of the material were also performed. HR AES measurements on bundles of different thicknesses were performed and compared. All the types of spectroscopy measurements were quantified, especially with respect to the Mo, S, and I. The Mo : S : I stoichiometries thus determined, deviated from the nominal value. It was also found that the stoichiometry is approximately constant along an individual nanowire bundle, but less so from one bundle to another. However, it was not possible to show conclusively that the diameter of the bundle influences the stoichiometry. The stoichiometry obtained from XPS measurements differs significantly from the one obtained from the AES measurement as well as from the nominal one. A possible explanation for the differences in the stoichiometries measured by AES, XPS, and the nominal values is the influence of the AES analysis on the sample and the interaction between the characteristics of XPS technique and the sample structure. Copyright © 2008 John Wiley & Sons, Ltd.

A study of composite and structural changes of particles prepared by coprecipitation in solutions of Cu2+ and Zn2+ salts at different starting molar ratios of the corresponding metal nitrates (4:1, 2:1, 1:1, 1:2, 1:4) in the presence of urea is described. The effects of the initial concentration ratios and the ageing time on the final product were discussed in some detail. The final solids were characterized by SEM–EDS, XRD. On ageing at 85°C, the change from initially amorphous particles to crystalline structure takes place and the results depend on the metal ratio used.

We present a new synthetic approach leading to the formation of polypyrrole architectures in submicron level and to silver/polypyrrole nanocomposites via an interfacial polymerization in a water/chloroform interface. The oxidizing agent was either Ag(I) or Fe(III). In the first case, silver nanoparticles resulted. The mean diameter of the polypyrrole structures is in the range of 200–300nm according to the addition or not of various surfactants. The progress of the reaction was studied by UV–visible spectroscopy, which also revealed the formation of a polaron band during the growth of the oligomers. The crystal structure of the polymers was examined by X ray diffractometry and all samples appeared to be amorphous, while the samples were further characterized by thermogravimetric analysis and FT-IR spectroscopy.

We report on the synthesis and characterization of new a nano-wire-like material with chemical formula Mo6S4.5I4.5. The material can be synthesized in a single step reaction from elements in bulk quantities. The material has a fur-like appearance and is composed of nanowires that are weakly bound in bundles. Bundles itself can be dispersed using an ultrasonic bath in various organic solvents and water. Elemental analysis, X-ray diffraction, thermal analysis (TG, DTA), and electron microscopy were used to characterize the new material in the shape of nanowires. Due to their monodisperse and metallic nature, molybdenum-sulphur-iodine nanowires are an interesting alternative to carbon nanotubes for some applications.