POTENTIAL-ENERGY CALCULATION AND CONDUCTIVITY MECHANISM IN NA3CR2P3O12 AND NA1+XZR2-XCRXP3O12

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Quantitative measurements of the CH radical in sooting diffusion flames at atmospheric pressure

The potential of Laser Induced Fluorescence detection of the CH radical using C–X (0–0) excitation is investigated in a sooting methane/air diffusion flame at atmospheric pressure. Fluorescence is detected using the very narrow (<0.4 nm) Q-branch of the C–X (0–0) band, which enables the measurement of CH in sooting flames without interference from PAH fluorescence and soot emissions. Absolute concentrations are obtained using Cavity Ring Down Spectroscopy. 1D CH profiles in the sooting zone are recorded using a CCD camera with an excellent signal-to-noise ratio. The C–X (0–0) excitation associated with Q-branch detection is shown to be three times more efficient than the B–X scheme

Investigation of the ability of the corrosion protection of Zn-Mg coatings

Presently Zn-Mg coatings are being developed as a contribution to next generation of galvanized steel. However, the underlying corrosion mechanism is still under debate. In this paper we show that Raman spectroscopy next to electrochemical methods (linear sweep voltammetry and electrochemical impedance spectroscopy) can successfully be used to help in identifying the corrosion products of Zn-Mg coated galvanized steel (ZMS) when dipped into 3 wt. % NaCl aqueous solution at ambient temperature (25 °C). The obtained results are compared to galvanized steel. This study reveals that in the case of ZMS, Mg is mainly anodically dissolved forming a compact layer of Mg(OH)2/MgO and MgCO3. It is believed that the formation of this compact layer and the insulating properties of MgO, due to its large band gap, are responsible for the increased corrosion resistance of the alloy

Study of thermal and optical properties of the Ge-Te-CdI(2)/ZnI(2) far infrared transmitting glasses

A systematic series of (100 - x)(GeTe4.3) - xCdI(2)/ZnI2 far infrared transmitting glasses were prepared by traditional melt-quenching method. ZnI2 (20 mol%) can be introduced in the glassy matrix, while only 10 mol % CdI2 can be incorporated in the Ge-Te-CdI2 glass system. Based on differential thermal analysis (DTA) data, most of the glass samples have good thermal stability. A maximum Delta T value of 115 degrees C was obtained for the glass composition 90(GeTe4.3)-10ZnI(2). The allowed indirect transition optical band gap was calculated according to the classical Tauc equation. It is found that the indirect optical band gap decreased from 0.619 to 0.569 eV with the CdI2 addition and increased from 0.628 to 0.677 eV with the ZnI2 addition. According to infrared transmission spectra, the Ge-Te-CdI2/ZnI2 glasses show wide IR transparency. (C) 2010 Elsevier B.V. All rights reserved.X1122sciescopu

Local structure of dilute aqueous DMSO solutions, as seen from molecular dynamics simulations

The information about the structure of dimethyl sulfoxide (DMSO)-water mixtures at relatively low DMSO mole fractions is an important step in order to understand their cryoprotective properties as well as the solvation process of proteins and amino acids. Classical MD simulations, using the potential model combination that best reproduces the free energy of mixing of these compounds, are used to analyze the local structure of DMSO-water mixtures at DMSO mole fractions below 0.2. Significant changes in the local structure of DMSO are observed around the DMSO mole fraction of 0.1. The array of evidence, based on the cluster and the metric and topological parameters of the Voronoi polyhedra distributions, indicates that these changes are associated with the simultaneous increase of the number of DMSO-water and decrease of water-water hydrogen bonds with increasing DMSO concentration. The inversion between the dominance of these two types of H-bonds occurs around XDMSO = 0.1, above which the DMSO-DMSO interactions also start playing an important role. In other words, below the DMSO mole fraction of 0.1, DMSO molecules are mainly solvated by water molecules, while above it, their solvation shell consists of a mixture of water and DMSO. The trigonal, tetrahedral, and trigonal bipyramidal distributions of water shift to lower corresponding order parameter values indicating the loosening of these orientations. Adding DMSO does not affect the hydrogen bonding between a reference water molecule and its first neighbor hydrogen bonded water molecules, while it increases the bent hydrogen bond geometry involving the second ones. The close-packed local structure of the third, fourth, and fifth water neighbors also is reinforced. In accordance with previous theoretical and experimental data, the hydrogen bonding between water and the first, the second, and the third DMSO neighbors is stronger than that with its corresponding water neighbors. At a given DMSO mole fraction, the behavior of the intensity of the high orientational order parameter values indicates that water molecules are more ordered in the vicinity of the hydrophilic group while their structure is close-packed near the hydrophobic group of DMSO. © 2017 Author(s)

Non-linear Raman effects and photodarkening in chalcogenide glass

The intensities of Raman-scattering bands in the spectrum of vitreous \chem{As_{2}S_{3}} assigned to vibrations of intrinsic homopolar As-As ( \sim 234\un{cm^{-1}}) and S-S ( \sim 490\un{cm^{-1}}) bonds increase much more with the power of the exciting laser than does the principle vibrational band which is related to As-S-As glass-network vibrations ( \sim 343\un{cm^{-1}}). In addition, the frequency of this glass-network vibration softens with an increase of the laser power. We ascribe these non-linear Raman effects to a photo-stimulated increase in polarizability of the homopolar bonds accompanied by softening of glass-network vibrations. It is suggested that this non-linearity is related to photodarkening in \chem{As_{2}S_{3}}