On understanding the effect of benzotriazole during barrier-film growth on Al-Cu alloys

Abstrasct The effect of benzotriazole on the growth of anodic films on aluminium and an Al-3.5 wt% Cu alloy has been examined by transmission electron microscopy (TEM) and electrochemical impedance spectroscopy (EIS). Films grown to relatively high voltages reveal flaws and oxygen-filled voids as a result of the surface morphology and copper enrichment and oxidation at the alloy/film interface. Benzotriazole, apart from increasing the efficiency of anodic film growth on the artificially aged alloy, also reduces the population density of the local features. The impedance response of films formed at relatively low voltages has been used to probe the early influence of benzotriazole on the macroscopic surface as well as flaws of the oxide-covered substrate.     

Numerical method for the KdV–Kawahara and Benney–Lin equations

We are concerned with the initial-boundary-value problem associated to the Korteweg – de Vries – Kawahara (KdVK) equation and Benney – Lin (BL) equation, which are transport equations perturbed by dispersive terms of 3rd and 5th order and a term of 4th order in the case of (BL) equation. These equations appear in several fluid dynamics problems. We obtain local smoothing effects that are uniform with respect to the size of the interval. We also propose a simple finite-difference scheme for the problem and prove its stability. Finally, we give some numerical examples. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)     

"H2-free" demethoxylation of guaiacol in subcritical water using Pt supported on N-doped carbon catalysts: A cost-effective strategy for biomass upgrading

"H2-free" HDO is a revolutionary route to circumvent the limitations of H2-fed HDO reactors for biomass upgrading.This work demonstrates the viability of this e...     

Polycaprolactone and poly-β-cyclodextrin polymer blend: a Biopolymers composite film for drug release

Nowadays, biomedical films containing drug carriers are preferred over conventional ones, since the protection of the injury and the therapy is joined within a single device. In the current work, we prepared polycaprolactone (PCL) composite films with β-cyclodextrin (βCD) or its epichlorohydrin crosslinked polymer (βCDP) as ibuprofen (Ibu) drug carrier. The composite films were prepared at different PCL/additive ratios (2, 5, 10 and 20 wt%). ATR-FTIR spectroscopy and water contact angle (WCA) measurements indicated a scarce presence of the additives on the surface. Cross-section scanning electron micrographs showed the presence of aggregates corresponding to βCD and βCDP in the inner regions of the films. The incorporation of βCD and βCDP into the PCL films did not affect their thermal properties as was determined from differential scanning calorimetry (DSC). PCL-films with 10 wt% of the inclusion complexes Ibu@βCD and Ibu@βCDP were prepared and the release studies were performed. At pH?=?7.2, PCL-Ibu@βCDP composite film released 55% of Ibu within the first six hours; eight times the amount released by PCL-Ibu@βCD within the same time interval. A plausible mechanism for ibuprofen release is discussed based on the cross-section SEM micrographs of composite films.

     

Ethanol steam reforming on Ni/Al2O3 catalysts: effect of the addition of Zn and Pt

Ni-based catalysts supported on Zn-modified alumina were investigated in the ethanol steam reforming reaction. A commercial γ-alumina was impregnated with different amounts of zinc nitrate (0, 2, 5, 10, 15, 20 wt.% on Zn basis), calcined, and then impregnated with nickel nitrate aqueous solutions. The samples were characterized by a number of techniques: N(2) adsorption at 77 K, X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray fluorescence (XRF), and temperature-programmed reduction (TPR). Their catalytic behavior in the ethanol steam reforming reaction was studied at 873 K, with a H(2)O/ethanol ratio of 5:1. Two effects of the presence of Zn were detected. On the one hand, zinc modifies the surface structure and the surface chemistry of the catalysts by formation of zinc aluminates, and on the other hand, zinc oxide can be reduced to metallic zinc under reaction conditions, thus modifying the catalytic properties of the active phase. The presence of Zn increases the ethanol conversion to gaseous compounds as compared with the catalyst supported on the Zn-free commercial alumina. The addition of a small amount of Pt (1 wt.%) causes a beneficial effect in the reaction. When Ni catalysts were used without a previous reduction treatment, ethylene was formed in high amounts; however, the Pt-Ni catalysts need no reduction pre-treatment to achieve high H(2) yields (close to 70%) and showed a high stability versus time on stream because of the control of the production of ethylene, a coke precursor.     

Effect of support and pre-treatment conditions on Pt-Sn catalysts: application to nitrate reduction in water

The effect of the support (activated carbon or titanium dioxide) on the catalytic activity and selectivity to nitrogen of Pt-Sn catalysts in nitrate reduction was studied. The effects of the preparation conditions and the Pt:Sn atomic ratio were also evaluated. It was observed that the support plays an important role in nitrate reduction and that different preparation conditions lead to different catalytic activities and selectivities. Generally, the catalysts supported on activated carbon were less active but more selective to nitrogen than those supported on titanium dioxide. The monometallic Pt catalyst is active for nitrate reduction only when supported on titanium dioxide, which is explained by the involvement of the support in the reaction mechanism. The catalysts were characterized by different techniques, and significant changes on metal chemical states were observed for the different preparation conditions used. Only metallic Pt and oxidized Sn were observed at low calcination and reduction temperatures, but some metallic Sn was also present when high temperatures were used, being also possible the formation of Pt-Sn alloys.     

A stable luminescent hybrid mesoporous copper complex-silica

Surfactant-assisted co-condensation of an emissive tetranuclear alkynyl-phosphine copper cluster with TEOS affords a hydrothermally stable blue-emitter mesoporous hybrid metal complex-silica material.     

Electron transfer reactions of 1-phenyl-4-vinylpyrazole mediated by cerium(IV) ammonium nitrate

Summary The title compound is converted into the cyclic ethers5 and the alcohol6 upon treatment with ceric ammonium nitrate in acetone. Using methanol as a solvent the dimethoxy derivative9 and the nitrate ester10 are formed. No cross cycloaddition is observed in the presence of olefins such as ethyl vinyl ether,DMAD, or indene; however, with cyclopentadiene as co-reagent a mixture of the exo-endo Diels-Alder adducts14 involving the vinylic system of 1 as 2 component is obtained. The results are rationalized through the interrnediacy of the radical cation1 ^·+, generated by single electron transfer (SET) from the neutral precursor1 to Ce(IV).

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Elektrontransfer-Reaktionen von 1-Phenyl-4-vinylpyrazol mittels Cer(IV)-Ammonnitrat

Zusammenfassung Die Titelverbindung wurde mittels Cer(IV)-Ammonnitrat in Aceton in die cyclischen Ether5 und den Alkohol6 umgewandelt. Mit Methanol als Lösungsmittel wurde das Dimethoxyderivat9 und der Nitratester10 gebildet. Bei Anwesenheit von Olefinen wie etwa Ethylvinylether,DMAD oder Inden wurden keine Cross-Cycloadditionen beobachtet. Hingegen wurde mit Cyclopentadien als Mitreagens eine Mischung vonexo-endo-Diels-Alder-Produkten14 erhalten, wobei das vinylische System von1 als 2-Komponente fungiert. Die Ergebnisse werden mittels eines intermediär auftretenden Radikalkation1 ^·+ als Produkt eines Einelektronentransfers (SET) des neutralen Vorläufers1 zu Ce(IV) rationalisiert.

     

A Novel Route to 5,7-Dimethoxy-6-hydroxyflavone

A novel route to 5,7-dimethoxy-6-hydroxyflavone is described, involving the cyclization of an intermediate phosphorane as the key step.