Untersuchung der Ausscheidungskinetik der Polymermischung aus deuteriertem Polystyrol (d-PS) und Polyvinylmethylether (PVME) mittels Neutronen-Kleinwinkel-Streuung

The scope of this work is the investigation of the system PVMEId-PS by small angle neutron scattering (SANS). The measurementswere done with a pinhole-camera and a high resolution double vrystal diffractometer and covered the resolution range from 10$^{-3}$ to 3 X 10$^{-2} \mathring{A}^{-1}$ and 2 x 10$^{-5}$ to 6 x 10$^{-4} \mathring{A}^{-1}$ respectively. As a basis for these investigations the phase diagram of a PVME/d-PS mixture was measured with SANS. The spinodal for different curve between stable and den-Liming region was obtained. For PVME with molecular weights M$_{\omega}$ = 60000 and d-PS with M$_{\omega}$ = 215103 the critical point is at the concentration $\Phi$ = 0.2. From the spinodal and the structure factor the $\textit{Flory-Huggins}$ parameter $\chi$ could be extracted as a function of temperature. It was found that $\chi$=0 for T$_{comp}$ = 135°C and $\chi$ is independent of the molecular weight within the accuracy of the data, thus $\chi$ may be associated with a local interaction parameter. The scattering experiments for the determination of the spinodal confirmed the mean-field behaviour of the critical scattering which was earlier found by $\textit{Herkt-Maetzky}$ and $\textit{Schelten}$. Further, the time dependence of the structur factor in the miscibility gap was investigated in the Q-range 2 x 10$^{-5} \mathring{A}^{-1} \le Q \le$ 10$^{-3} \mathring{A}^{-1}$. From the structure factors, specially from the position Q$_{max}$ of their maxima, a characteristic length was extracted. It's time dependence follows the power law $Q^{-1}_{max} \varpropto$ t for t > 100 sec. For smaller t a behaviour similiar to the prediction of $\textit{Cahn - Hilliard}$ was observed, i.e. no shift of the peak in the structur factor with increasing time

Removal of Reactive Black 5 from aqueous solution by ozone for water reuse in textile dyeing processes

The removal of textile dye Reactive Black 5 from aqueous solution by ozone until total decolorization using a semi-batch bubbling reactor was studied. This compound was selected because of its extended industrial application for cotton dyeing. Decomposition of that textile dye was observed by adding some chemical auxiliaries commonly used in textile dyeing processes such as sodium sulfate, sodium carbonate and sodium hydroxide, between the limits found in a normal dyehousewastewater. The recording ofUV–Vis spectrawas used to evaluate the dye decomposition rate. The decomposition rate through this treatment depends on the presence of dyeing auxiliaries. Color disappears for 10 min of ozone treatment when auxiliaries are present. The treated water was then used in dyeing of cotton samples with a set of reactive dyes and direct dyes, separately, until 5 times without further salt addition, in order to evaluate the feasibility to reuse taking advantage of the present salt. For short times of solution ozonation, byproducts accumulation was observed by UV–Vis spectroscopy. The influence of byproducts generated during ozonation of dye solutions on the coloration quality of the water recirculation depends on the nature of dyes used in dyeing processes. The preservation of sodium ions, responsible for the zeta potential neutralization in dyeing process, was demonstrated using atomic absorption spectroscopy. © 2010 Elsevier B.V. All rights reserve

Síntesis y caracterización de nanopartículas Fe3O4@SiO2

Reportamos la caracterización de dos metodologías para la deposición de una película delgada de SiO2 sobre un núcleo superparamagnético de Fe3O4. Se comprobó a través de Difracción de rayos-X que la fase estructural sintetizada era magnetita. Adicionalmente se presenta un análisis de las propiedades magnéticas empleando Espectroscopía Mössbauer y un análisis del acoplamiento molecular de la película con el sustrato por Espectroscopía de infrarrojo. El análisis de los datos obtenidos nos permite identificar como método óptimo aquel que emplea POE5

On the changes and reactions in metal oxides under microwave irradiation

Metal oxides are the starting point to obtain many ceramic materials and the microwave heating an appropiate preparative route for their sintering or boundary joining, particularly in those cases where at least one component shows an efficient microwave energy absorption [1–4]. The microwave heating takes place via dielectric losses, through a complex process in which the electromagnetic fields of the incident radiation induce motions of electrons and ions and rotate charge systems such as dipoles. The resistance to these induced motions results in an internal volumetric heating, with a reversal thermal gradient and flow of heat compared to conventional heating methods (convection and conduction) [5, 6]. This opens the possibility of a rapid and selective heating of a component in a given mixture of phases [7, 8]. These and many other applications of the microwave heating for the preparation of metal oxides-based materials are supported in a knowledge of the microwave irradiation effects on the properties of single metal oxides. In a study in this sense we have noted that under microwave irradiation many metal oxides behave as already established, however, in some cases different or not reported results were found, which are discussed in this contribution

Redetermination of 1-cyclohexyl-3-(2-furoyl)thiourea

The title compound, C12H16N2O2S, was synthesized from furoyl isothiocyanate and cyclohexylamine in dry acetone, and the crystal structure redetermined. The thiourea group is in the thioamide form. The structure [Otazo-Sánchez et al. (2001). J. Chem. Soc. Perkin Trans. 2, pp. 2211–2218] has been redetermined in order to establish the intra- and intermolecular interactions. The trans–cis geometry of the thiourea group is stabilized by intramolecular hydrogen bonding between the carbonyl and cis-thioamide groups, resulting in a pseudo-S(6) planar ring which makes a dihedral angle of 3.24 (6)° with the 2-furoyl group and a torsion angle of −84.3 (2)° with the cyclohexyl group. There is also an intramolecular hydrogen bond between the furan O atom and the other thioamide H atom. In the crystal structure, molecules are linked by intermolecular N—H...O hydrogen bonds, forming chains along [010]

Determinación estructural de Hexacianoferratos y Hexacianocobaltatos de Metales Alcalinotérreos

En el presente trabajo se lleva a cabo el estudio estructural de los Hexacianoferratos (III) y Hexacianocobaltatos (III) de metales alcalinotérreos (Mg, Ca, Sr, Ba). Estos materiales se caracterizaron por: Espectroscopía IR, Termogravimetría, Espectroscopía Mössbauer y Difracción de Rayos X. Empleando espectroscopía de infrarrojo se observa que los espectros presentan las bandas de absorción características ν(CN) (alrededor de 2180cm-1), así como las bandas ν(OH) en 3600-3300 cm-1. Por espectroscopía Mössbauer se obtuvo información estructural acerca del ambiente local de los átomos de hierro en los Hexacianoferratos, teniendo como resultado la asignación del doblete Fe(III) en los Espectros. Difracción de RX se utilizara como herramienta principal para realizar la determinación estructural de los materiales estudiados