Enthalpie de formation de la whitlockite Ca18Mg2H2(PO4)14

Pure and well crystallised whitlockite Ca₁₈Mg₂H₂(PO₄)₁₄ has been synthesized by precipitation from the magnesium and calcium nitrates and the diammonic phosphate. The product of the reaction has been characterized by X-ray diffraction, IR spectroscopy and chemical analysis. Using differential conduction calorimeters the enthalpies of solution of the whitlockite and of a mixture of the solid reactants - the tricalcium, the trimagnesium and the dicalcium phosphates - have been measured at 25°C for various concentrations of solid in a 46 wt% nitric acid solution. A combination of the enthalpies of solution with the enthalpies of formation of the reactants allows us to determine the standard enthalpy of formation of the whitlockite. The value deduced, -27,93·10³kJ mol^-1, is compared to the standard enthalpies of formation of the trimagnesium and the tricalcium phosphates. This revised version was published online in August 2006 with corrections to the Cover Date.     

A comparative study of a direct and pulse electrodeposition method of TiO2 films and its effect on photoelectrocatalytic degradation of methyl orange dye

The present study reports the titanium dioxide (TiO2) films synthesized from TiCl3 precursor on ITO glass substrates using two electrochemical techniques, namely direct electro-deposition (DE) and pulse electro-deposition (PE). The synthesis potential during the time-on (Ton) period was fixed at ?1.5 V. However, the open-circuit potential was applied during the time-off (Toff) period. The effect of the technique of electro-deposition and Toff duration on the properties of TiO2 films and their photoelectron-catalytic activity were investigated. The obtained films were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), UV-VIS spectrometer, and photocurrent measurement respectively. It is found that the use of the PE technique at different Toff improves the properties of TiO2 films compared to the DE technique. The XRD patterns show the anatase phase with a marked preferential orientation along the (101) direction for all samples. From the SEM analysis, it is seen a significant change from big multigrain agglomerates at DE to a dense film structure and small multigrain agglomerates at different Toff. As the Toff decreases from 3 s to 1 s, the photocurrent response rises and reaches a high value of about 12 mA/cm2. Compared with DE, and under UV light the photocatalytic property of TiO2 film synthesis via PE has been improved in the degradation of methyl orange (MO). Finally, the films deposited at low Toff (Toff =1 s) show a faster degradation of MO.     

Remediation of copper ions from aqueous solution using hybrid magadiite: kinetics,isotherm and mechanism of removal

Research on Chemical Intermediates - This paper deals with the potential use of hybrid magadiite composite as an alternative adsorbent for the removal of copper ions. Na-magadiite was synthesized...     

Synthesis,characterization and study of methyl 3-(2-oxo-2H-1,4-benzoxazin-3-yl) propanoate as new corrosion inhibitor for carbon steel in 1M H2SO4 solution

Research on Chemical Intermediates - A new benzoxazin derivative, namely methyl 3-(2-oxo-2H-1,4-benzoxazin-3-yl) propanoate (1,4-MBXP), was synthesized under mild conditions from 2-aminophenols and...     

Electrochemical determination of Cd<Superscript>2+</Superscript> at a titanium electrode modified with a lead film by square wave anodic stripping voltammetry

The modified titanium electrode with lead film (PbTiE) was used for determination of trace levels of cadmium using square wave anodic stripping voltammetry (SWASV). The measurement of cadmium on the PbTiE has the best reply under the following conditions of PbTiE preparation: 10^–3 mol L^–1 Pb²⁺ in HCl (pH 1.0), deposition potential of–1.40 V vs. Ag/AgCl/KCl_sat and deposition time of 300 s. The PbTiE reveals highly linear behavior in the concentration range 5 × 10^–8 to 10^–6 mol L^–1, with a limit of detection of 2 × 10^–9 mol L^–1. Interference of nine ionic species was evaluated. The measurements were carried out without removing dissolved oxygen from the solution.     

Étude expérimentale du dépôt de particules colloïdales en milieu poreux : Influence de l'hydrodynamique et de la salinité

This study deals with colloid transport in porous media which applications are found in subsurface water, petroleum engineering or civil engineering. An experimental study of colloidal polystyrene Latex particles deposition in a consolidated porous medium is presented. The influence of ionic strength of the colloid suspension and the flow rate on particle deposition is investigated. We see first that beyond a critical salt concentration, the total collector efficiency increases with the ionic strength. Moreover, such collector efficiency decreases as the flow rate increases according to theory. In other respects, using a γ ray attenuation technique allows us to measure local porosity fluctuation due to particles deposition. By this way deposition kinetics may be followed locally and precisely. Nevertheless when considering the thickness of the adsorbed layer over large scales, obtained results using the γ rays attenuation technique are found in good agreement with those obtained by means of an usual technique especially at latest stages of adsorption process. To cite this article: A. Djehiche et al., C. R. Mecanique 337 (2009).     

Antifungal activities of amino acid ester functional pyrazolyl compounds against Fusarium oxysporum f.sp. albedinis and Saccharomyces cerevisiae yeast

Series of functional multidendate ligands based on pyrazole and amino acid derivatives were prepared in good and excellent yields (75–5%) by condensation of one equivalent of amino acid ester hydrochloride substrates with two equivalents of (3,5-dimethyl-1H–pyrazol-1-yl)methanol. These tridentate functionalized compounds and their starting materials were screened for their antifungal activities against Fusarium oxysporum f.sp. albedinis and the yeast of Saccharomyces cerevisiae. Considerable activities were recorded with respect to the two studied microorganisms.     

Phase behavior of polystyrene acrylonitril copolymer and polymethylmethacrylate blends under shear

Polymer blends undergo external stresses such as pressure and shear in course of processing cycles. The knowledge of their phase behavior at each step of these cycles is crucial for understanding their physical properties and eventually improves their performance in practical applications. The effects of shear on the phase diagram of binary polymer blends are considered. A theoretical formulism is used upon which the free energy is the sum of two terms. The first term is modeled with the Flory–Huggins free energy of mixing and describes the thermodynamic behavior of the system in the quiescent state. The second term represents the excess free energy stored during flow. In the presence of shear flow, the excess free energy is expressed in terms of the viscosity and the shear modulus. Both quantities depend on composition and shear rate. The curvature of the variation of viscosity versus composition has a tremendous impact upon the nature of phase separation. Phase diagrams are described by the spinodal curves and show for the case considered here miscibility enhancement with increasing shear rate. A good correlation is found with experimental data of the literature on blends of polystyrene acrylonitril copolymer and polymethylmethacrylate. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2011     

Calibration transfer of near‐IR partial least squares property models of fuels using virtual standards

Partial least squares (PLS) models of 10 important jet and diesel fuel properties were built using spectra from a master near‐IR dispersive instrument and then subsequently transferred to a secondary dispersive instrument via a novel calibration transfer method using virtual standards and a slope‐bias correction. Implementation of the transfer requires that only seven spectra of neat solvents be acquired on the master and secondary instruments. The spectra of the neat solvents are then used to digitally replicate spectra from the calibration set to generate virtual standards. Comparison of PLS predictions for the master and secondary instrument virtual standards provides a simple but effective slope‐bias correction for transfer. The transferred fuel properties include American Petroleum Institute gravity, % aromatics, cetane index, flashpoint, hydrogen content, % saturates, and distillation temperatures at 10%, 20%, 50%, and 90% volume recovered. Transfer error was lower than using either the pure solvents with a slope‐bias correction or than using a piecewise direct standardization calibration transfer using fuel spectra. Transfer error was higher than when using actual fuels to transfer the calibration. The use of virtual standards eliminates the need to maintain either complex fuel standards or the master instrument for future instrument calibration transfers. Copyright © 2011 John Wiley & Sons, Ltd.